Resist composition and method of forming resist pattern

ABSTRACT

A method of forming a resist pattern, including forming a resist film by coating a resist composition including a base component (A) that exhibits increased solubility in an alkali developing solution, a photo-base generator component (C) that generates a base upon exposure, an acid supply component (Z) and a compound (F) containing at least one selected from the group consisting of a fluorine atom and a silicon atom and containing no acid decomposable group which exhibits increased polarity by the action of acid on a substrate; subjecting the resist film to exposure baking the exposed resist film; and subjecting the resist film to alkali development, thereby forming a negative-tone resist pattern.

This application is a continuation of U.S. patent application Ser. No.13/624,639, filed Sep. 21, 2012, which claims priority to JapanesePatent Application Nos. 2011-207772, 2011-208136 and 2011-208147, all ofwhich were filed Sep. 22, 2011, the contents of which are incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates to a method of forming a resist pattern inwhich a negative resist pattern is formed by developing with an alkalideveloping solution, and a resist composition used therein.

BACKGROUND ART

Techniques (pattern-forming techniques) in which a fine pattern isformed on top of a substrate, and a lower layer beneath that pattern isthen fabricated by conducting etching with this pattern as a mask arewidely used in the production of semiconductor devices and liquidcrystal display devices. These types of fine patterns are usually formedfrom an organic material, and are formed, for example, using alithography method or a nanoimprint method or the like. In a lithographymethod, for example, a resist film is formed on a support such as asubstrate using a resist material containing a base component such as aresin, and the resist film is then subjected to selective exposure ofradial rays such as light or electron beam, followed by development,thereby forming a resist pattern having a predetermined shape on theresist film. Using this resist pattern as a mask, a semiconductor deviceor the like is produced by conducting a step in which the substrate isprocessed by etching.

The aforementioned resist materials can be classified into a positivetype and a negative type. A resist material in which the exposedportions exhibit increased solubility in a developing solution is calleda positive type, and a resist material in which the exposed portionsexhibit decreased solubility in a developing solution is called anegative type.

In general, an aqueous alkali solution (alkali developing solution) suchas an aqueous solution of tetramethylammonium hydroxide (TMAH) is usedas the developing solution. Alternatively, organic solvents such asaromatic solvents, aliphatic hydrocarbon solvents, ether solvents,ketone solvents, ester solvents, amide solvents and alcohol solvents areused as the developing solution (for example, see Patent Documents 1 and2).

In recent years, advances in lithography techniques have led to rapidprogress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength (increasing the energy) of the exposure light source.Conventionally, ultraviolet radiation typified by g-line and i-lineradiation has been used, but nowadays KrF excimer lasers and ArF excimerlasers are now starting to be introduced in mass production.Furthermore, research is also being conducted into lithographytechniques that use an exposure light source having a wavelength shorter(energy higher) than these excimer lasers, such as electron beam (EB),extreme ultraviolet radiation (EUV), and X ray.

As shortening of the wavelength of the exposure light source progresses,it is required to improve various lithography properties of the resistmaterial, such as the sensitivity to the exposure light source and theresolution capable of reproducing patterns of minute dimensions. Asresist materials which satisfy such requirements, chemically amplifiedresists are known.

As a chemically amplified resist, a composition is generally used, whichincludes a base component that exhibits a changed solubility in adeveloping solution under the action of acid and an acid generatorcomponent that generates acid upon exposure. For example, when the abovedeveloping solution is an alkali developing solution (when the processis an alkali developing process), as the base component, a basecomponent that exhibits increased solubility in an alkali developingsolution by the action of acid is used.

Conventionally, a resin (base resin) is mainly used as the basecomponent of a chemically amplified resist composition. Currently,resins that contain structural units derived from (meth)acrylate esterswithin the main chain (acrylic resins) are the mainstream as base resinsfor chemically amplified resist compositions that use ArF excimer laserlithography, as they exhibit excellent transparency in the vicinity of193 nm.

Here, the term “(meth)acrylic acid” is a generic term that includeseither or both of acrylic acid having a hydrogen atom bonded to theα-position and methacrylic acid having a methyl group bonded to theα-position. The term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position. The term “(meth)acrylate” is a genericterm that includes either or both of the acrylate having a hydrogen atombonded to the α-position and the methacrylate having a methyl groupbonded to the α-position.

In general, the base resin contains a plurality of structural units forimproving lithography properties and the like. For example, a structuralunit having a lactone structure and a structural unit having a polargroup such as a hydroxy group are used, as well as a structural unithaving an acid decomposable group which is decomposed by the action ofan acid generated from the acid generator to form an alkali solublegroup (for example, see Patent Document 3). When the base resin is anacrylic resin, as the acid decomposable group, in general, resins inwhich the carboxy group of (meth)acrylic acid or the like is protectedwith an acid dissociable group such as a tertiary alkyl group or anacetal group are used.

As a technique for further improving the resolution, a lithographymethod called liquid immersion lithography (hereafter, frequentlyreferred to as “immersion exposure”) is known in which exposure(immersion exposure) is conducted in a state where the region betweenthe lens and the resist layer formed on a wafer is filled with a solvent(a immersion medium) that has a larger refractive index than therefractive index of air (see for example, Non-Patent Document 1).

According to this type of immersion exposure, it is considered thathigher resolutions equivalent to those obtained using a shorterwavelength light source or a larger NA lens can be obtained using thesame exposure light source wavelength, with no lowering of the depth offocus. Furthermore, immersion exposure can be conducted by applying aconventional exposure apparatus. As a result, it is expected thatimmersion exposure will enable the formation of resist patterns ofhigher resolution and superior depth of focus at lower costs.Accordingly, in the production of semiconductor devices, which requiresenormous capital investment, immersion exposure is attractingconsiderable attention as a method that offers significant potential tothe semiconductor industry, both in terms of cost and in terms oflithography properties such as resolution.

Immersion exposure is effective in forming patterns having variousshapes. Further, immersion exposure is expected to be capable of beingused in combination with currently studied super-resolution techniques,such as phase shift method and modified illumination method. Currently,as the immersion exposure technique, technique using an ArF excimerlaser as an exposure source is being actively studied. Further, water ismainly used as the immersion medium.

Because it is necessary to impart water repellency to the obtainedresist film in the immersion exposure, resist compositions for immersionexposure which contain a fluorine-containing compound have been reported(see, for example, Non-Patent Document 1).

Active research and development of fluorine-containing compounds havebeen conducted in various fields including the resist materials forimmersion exposure described above for their properties such as waterrepellency and transparency. For example, in the field of resistmaterials, fluorine-containing polymers that include a structural unitcontaining a fluorine atom have been used in recent years (see PatentDocument 4). Examples of the Patent Document 4 show that the specificfluorine-containing compound contributes to the defect reduction in theformation of the pattern using the immersion exposure, but is notlimited therein. It is known that fluorine-containing compoundscontribute to improvement of lithography properties such as the defectreduction (see Patent Documents 5 and 6).

As a lithography technique which has been recently proposed, a doublepatterning method is known in which patterning is conducted two or moretimes to form a resist pattern (for example, see Non-Patent Documents 2and 3). There are several different types of double patterning process,for example, (1) a method in which a lithography step (from applicationof resist compositions to exposure and developing) and an etching stepare performed twice or more to form a pattern and (2) a method in whichthe lithography step is successively performed twice or more. Accordingto the double patterning method, a resist pattern with a higher level ofresolution can be formed, as compared to the case where a resist patternis formed by a single lithography step (namely, a single patterningprocess), even when a light source with the same exposure wavelength isused, or even when the same resist composition is used. Furthermore,double patterning process can be conducted using a conventional exposureapparatus.

Moreover, a double exposure process has also been proposed in which aresist film is formed, and the resist film is subjected to exposuretwice or more, followed by development to form a resist pattern (forexample, see Patent Document 7). Like the double patterning processdescribed above, this type of double exposure process is also capable offorming a resist pattern with a high level of resolution, and also hasan advantage in that fewer number of steps is required than theabove-mentioned double patterning process.

In a positive tone development process using a positive type, chemicallyamplified resist composition (i.e., a chemically amplified resistcomposition which exhibits increased alkali solubility in an alkalideveloping solution upon exposure) in combination with an alkalideveloping solution, as described above, the exposed portions of theresist film are dissolved and removed by an alkali developing solutionto thereby form a resist pattern. The positive tone process using acombination of a positive chemically amplified resist composition and analkali developing solution is advantageous over a negative tonedevelopment process in which a negative type, chemically amplifiedresist composition is used in combination with an alkali developingsolution in that the structure of the photomask can be simplified, asatisfactory contrast for forming an image can be reliably obtained, andthe characteristics of the formed resist pattern are excellent. Forthese reasons, currently, positive-tone development process using acombination of a positive chemically amplified resist composition and analkali developing solution is mainly employed in the formation of anextremely fine resist pattern.

DOCUMENTS OF RELATED ART Patent Documents

-   [Patent Document 1] Japanese Unexamined Patent Application, First    Publication No. Hei 6-194847-   [Patent Document 2] Japanese Unexamined Patent Application, First    Publication No. 2009-025723-   [Patent Document 3] Japanese Unexamined Patent Application, First    Publication No. 2003-241385-   [Patent Document 4] Japanese Unexamined Patent Application, First    Publication No. 2010-277043-   [Patent Document 5] Japanese Unexamined Patent Application, First    Publication No. 2011-008001-   [Patent Document 6] Japanese Unexamined Patent Application, First    Publication No. 2011-128226-   [Patent Document 7] Japanese Unexamined Patent Application, First    Publication No. 2010-040849

Non-Patent Documents

-   [Non-Patent Document 1] Proceedings of SPIE (U.S.), vol. 5754, pp.    119-128 (2005)-   [Non-Patent Document 2] Proceedings of SPIE (U.S.), vol. 5256, pp.    985-994 (2003)-   [Non-Patent Document 3] Proceedings of SPIE (U.S.), vol. 6153, pp.    615301-1-19 (2006)

SUMMARY OF THE INVENTION

However, as further progress is made in lithography techniques and theapplication field for lithography techniques expands, furtherimprovement in various lithography properties is demanded in apositive-tone developing process using a combination of a positivechemically amplified resist composition and an alkali developingsolution.

For example, in the formation of an extremely small pattern (such as anisolated trench pattern, an extremely small, dense contact hole pattern,or the like), a region where the optical strength becomes weak (regionwhere irradiation by exposure is not satisfactorily reached) is likelyto be generated especially in the film thickness direction of the resistfilm, thereby deteriorating the resolution of the resist pattern.

In the formation of the aforementioned extremely small pattern, a methodof forming a resist pattern (negative pattern) in which regions wherethe optical strength becomes weak are selectively dissolved and removedis useful. As a method for forming a negative pattern using a chemicallyamplified resist composition used in a positive-tone developing processwhich is the mainstream, a method in which a developing solutioncontaining an organic solvent (organic developing solution) is used incombination with a chemically amplified resist composition is known.However, negative-tone developing process using an organic developingsolution is inferior to a positive-tone developing process using analkali developing solution in combination with a chemically amplifiedresist composition in terms of environment, apparatus and cost.Therefore, a novel method of forming a resist pattern is required whichis capable of forming the negative pattern with high contrast image.

In addition, resist compositions are required to improve not onlylithography properties but also storage stability. Specifically, theresist compositions are required which are capable of obtainingexcellent lithography properties or the like, even when patterns areformed using a resist composition stored for a certain period afterpreparing the resist composition, similarly when patterns are formedusing a resist composition, without storage, immediately after preparingthe resist composition.

The present invention takes the above circumstances into consideration,with an object of providing a method of forming a resist pattern whichenables the formation of the negative pattern, a novel method of forminga negative resist pattern using a resist composition having an excellentstorage stability, and a resist composition which can be used thereinand having an excellent storage stability.

As a result of intensive studies, the present inventors have invented amethod of forming a negative pattern in which a resist film formed by aresist composition containing a base component that exhibits increasedsolubility in an alkali developing solution by the action of an acid hasthe exposed portions remaining and the unexposed portions dissolved andremoved by an “alkali developing solution” (see Japanese PatentApplication No. 2011-106577). Subsequently, as a result of furtherintensive studies, the present inventors have found a resist compositionwhich has excellent storage stability for use of a fluorine-containingcompound and which is suitable for using in a method of forming thenegative pattern. The present invention has been completed based on thisfinding. In addition, the present inventors have found a resistcomposition which can be used in a method of forming the negativepattern and having excellent storage stability. The present inventionhas been completed based on this finding.

Specifically, a first aspect of the present invention is a resistcomposition including a base component (A) that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component (C) that generates a base upon exposure,an acid supply component (Z) and a compound (F) containing at least oneselected from the group consisting of a fluorine atom and a siliconatom, and the resist composition used in a method of forming a resistpattern which includes: a step (1) in which a resist film is formed bycoating the resist composition on a substrate; a step (2) in which theresist film is subjected to exposure; a step (3) in which baking isconducted after the step (2), such that, at an exposed portion of theresist film, the base generated from the photo-base generator component(C) upon the exposure and an acid derived from the acid supply component(Z) are neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acid derived from the acid supplycomponent (Z); and a step (4) in which the resist film is subjected toan alkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved, wherein the resist composition is used in the step (1) of themethod of forming a resist pattern, wherein the compound (F) contains noacid decomposable group which exhibits increased polarity by the actionof acid.

A second aspect of the present invention is a method of forming a resistpattern including: a step (1) in which a resist film is formed bycoating a resist composition which includes a base component (A) thatexhibits increased solubility in an alkali developing solution under theaction of acid, a photo-base generator component (C) that generates abase upon exposure, an acid supply component (Z) and a compound (F)containing at least one selected from the group consisting of a fluorineatom and a silicon atom, and containing no acid decomposable group whichexhibits increased polarity by the action of acid, on a substrate; astep (2) in which the resist film is subjected to exposure; a step (3)in which baking is conducted after the step (2), such that, at anexposed portion of the resist film, the base generated from thephoto-base generator component (C) upon the exposure and an acid derivedfrom the acid supply component (Z) are neutralized, and at an unexposedportion of the resist film, the solubility of the base component (A) inan alkali developing solution is increased by the action of the acidderived from the acid supply component (Z); and a step (4) in which theresist film is subjected to an alkali development, thereby forming anegative-tone resist pattern in which the unexposed portion of theresist film has been dissolved and removed.

A third aspect of the present invention is a resist compositionincluding a base component (A) that exhibits increased solubility in analkali developing solution under the action of acid, a photo-basegenerator component (C) that generates a base upon exposure, an acidiccompound component (G) and an amine (D), and the resist composition usedin a method of forming a resist pattern which includes: a step (1) inwhich a resist film is formed by coating the resist composition on asubstrate; a step (2) in which the resist film is subjected to exposure;a step (3) in which baking is conducted after the step (2), such that,at an exposed portion of the resist film, the base generated from thephoto-base generator component (C) upon the exposure and the acidiccompound component (G) are neutralized, and at an unexposed portion ofthe resist film, the solubility of the base component (A) in an alkalideveloping solution is increased by the action of the acidic compoundcomponent (G); and a step (4) in which the resist film is subjected toan alkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved, wherein the resist composition is used in the step (1) of themethod of forming a resist pattern, wherein the amount of the amine (D)is 1 mol or more, per 1 mol of the acidic compound component (G).

A fourth aspect of the present invention is a method of forming a resistpattern including: a step (1) in which a resist film is formed bycoating a resist composition which includes a base component (A) thatexhibits increased solubility in an alkali developing solution under theaction of acid, a photo-base generator component (C) that generates abase upon exposure, an acidic compound component (G) and an amine (D),the amount of which is 1 mol or more, per 1 mol of the acidic compoundcomponent (G), on a substrate; a step (2) in which the resist film issubjected to exposure; a step (3) in which baking is conducted after thestep (2), such that, at an exposed portion of the resist film, the basegenerated from the photo-base generator component (C) upon the exposureand the acidic compound component (G) are neutralized, and at anunexposed portion of the resist film, the solubility of the basecomponent (A) in an alkali developing solution is increased by theaction of the acidic compound component (G); and a step (4) in which theresist film is subjected to an alkali development, thereby forming anegative-tone resist pattern in which the unexposed portion of theresist film has been dissolved and removed.

A fifth aspect of the present invention is a resist compositionincluding a base component (A) that exhibits increased solubility in analkali developing solution under the action of acid, a photo-basegenerator component (C) that generates a base upon exposure, and anacidic compound component (G), and the resist composition used in amethod of forming a resist pattern which includes: a step (1) in which aresist film is formed by coating the resist composition on a substrate;a step (2) in which the resist film is subjected to exposure; a step (3)in which baking is conducted after the step (2), such that, at anexposed portion of the resist film, the base generated from thephoto-base generator component (C) upon the exposure and the acidiccompound component (G) are neutralized, and at an unexposed portion ofthe resist film, the solubility of the base component (A) in an alkalideveloping solution is increased by the action of the acidic compoundcomponent (G); and a step (4) in which the resist film is subjected toan alkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved, wherein the resist composition is used in the step (1) of themethod of forming a resist pattern, wherein the acidic compoundcomponent (G) includes a compound (G1C) composed of anitrogen-containing cation having a pKa value of 7 or less and acounteranion.

A sixth aspect of the present invention is a method of forming a resistpattern including: a step (1) in which a resist film is formed bycoating a resist composition which includes a base component (A) thatexhibits increased solubility in an alkali developing solution under theaction of acid, a photo-base generator component (C) that generates abase upon exposure, and an acidic compound component (G) including acompound (G1C) composed of a nitrogen-containing cation having a pKavalue of 7 or less and a counteranion, on a substrate; a step (2) inwhich the resist film is subjected to exposure; a step (3) in whichbaking is conducted after the step (2), such that, at an exposed portionof the resist film, the base generated from the photo-base generatorcomponent (C) upon the exposure and the acidic compound component (G)are neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acidic compound component (G); and a step(4) in which the resist film is subjected to an alkali development,thereby forming a negative-tone resist pattern in which the unexposedportion of the resist film has been dissolved and removed.

In the present description and claims, the term “aliphatic” is arelative concept used in relation to the term “aromatic”, and defines agroup or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalentsaturated hydrocarbon groups, unless otherwise specified. The sameapplies for the alkyl group within an alkoxy group.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon groups, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group are substituted with a halogen atom,and a “halogenated alkylene group” is a group in which part or all ofthe hydrogen atoms of an alkylene group are substituted with a halogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom.

A “hydroxyalkyl group” is a group in which part or all of the hydrogenatoms within an alkyl group have been substituted with a hydroxyl group.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (namely, a resin, polymer orcopolymer).

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

According to the present invention, there is provided a method offorming a resist pattern which enable formation of the negative pattern,and a resist composition which can be used therein and having excellentstorage stability.

Further, according to the present invention, there are provided a resistcomposition which can be used for formation of the negative pattern byusing a resist composition including a base component that exhibitsincreased solubility in an alkali developing solution under the actionof acid in an alkali developing process and which has an excellentstorage stability, and a method of forming a pattern using the resistcomposition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an advancing angle (θ₁) a receding angle(θ₂) and a sliding angle (θ₃).

FIG. 2A to FIG. 2D are schematic diagrams showing an example of oneembodiment of the method of forming a resist pattern according to thepresent invention.

MODE FOR CARRYING OUT THE INVENTION Resist Composition

The resist composition of the first aspect of the present invention isused in a step (1) of a method of forming a resist pattern including:the step (1) in which a resist film is formed by coating a resistcomposition which includes a base component that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component that generates a base upon exposure, anacid supply component and a compound (F) containing at least oneselected from the group consisting of a fluorine atom and a siliconatom, on a substrate; a step (2) in which the resist film is subjectedto exposure; a step (3) in which baking is conducted after the step (2),such that, at an exposed portion of the resist film, the base generatedfrom the photo-base generator component upon the exposure and an acidderived from the acid supply component are neutralized, and at anunexposed portion of the resist film, the solubility of the basecomponent in an alkali developing solution is increased by the action ofthe acid derived from the acid supply component; and a step (4) in whichthe resist film is subjected to an alkali development, thereby forming anegative-tone resist pattern in which the unexposed portion of theresist film has been dissolved and removed.

That is, the resist composition of the first aspect of the presentinvention includes a base component (hereafter, referred to as“component (A)”) that exhibits increased solubility in an alkalideveloping solution under the action of acid, a photo-base generatorcomponent (hereafter, referred to as “component (C)”) that generates abase upon exposure, an acid supply component (hereafter, referred to as“component (Z)”) and a compound (F) (hereafter, referred to as“component (F)”) containing at least one selected from the groupconsisting of a fluorine atom and a silicon atom, and is used in thestep (1).

The method of forming a resist pattern including the steps (1) to (4)will be described in the second aspect of the present inventiondescribed later.

The resist composition of the third aspect of the present invention isused in a step (1) of a method of forming a resist pattern including: astep (1) in which a resist film is formed by coating a resistcomposition which includes a base component (A) that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component (C) that generates a base upon exposure,an acidic compound component (G) and an amine (D), on a substrate; astep (2) in which the resist film is subjected to exposure; a step (3)in which baking is conducted after the step (2), such that, at anexposed portion of the resist film, the base generated from thephoto-base generator component (C) upon the exposure and the acidiccompound component (G) are neutralized, and at an unexposed portion ofthe resist film, the solubility of the base component (A) in an alkalideveloping solution is increased by the action of the acidic compoundcomponent (G); and a step (4) in which the resist film is subjected toan alkali development, thereby forming a negative-tone resist pattern inwhich the unexposed portion of the resist film has been dissolved andremoved.

That is, the resist composition of the third aspect of the presentinvention includes a base component (A) that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component (C) that generates a base upon exposure,an acidic compound component (G) (hereafter, referred to as “component(G)”) and an amine (D) (hereafter, referred to as “component (D)”). Themethod of forming a resist pattern, in which the resist composition ofthe third aspect of the present invention can be used, including thesteps (1) to (4) will be described in the fourth aspect of the presentinvention described later.

The resist composition of the fifth aspect of the present invention isused in a step (1) of a method of forming a resist pattern, in which aresist composition including a base component (A) that exhibitsincreased solubility in an alkali developing solution under the actionof acid, a photo-base generator component (C) that generates a base uponexposure, and an acidic compound component (G) is used, including thesteps (1) to (4) according to the fourth aspect of the presentinvention.

That is, the resist composition of the fifth aspect of the presentinvention includes a base component (A) that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component (C) that generates a base upon exposure,and an acidic compound component (G). The method of forming a resistpattern, in which the resist composition of the fifth aspect of thepresent invention can be used, including the steps (1) to (4) will bedescribed in the sixth aspect of the present invention described later.

In the present invention, a “negative-tone resist pattern” refers to aresist pattern in which an unexposed portion of the resist film isdissolved and removed by an alkali developing solution, and an exposedportion remains as a pattern. A resist composition which forms thenegative resist pattern is frequently referred to as a “negative resistcomposition”. In particular, the resist composition of the presentinvention is the negative resist composition.

Base Component; Component (A)

The component (A) is a base component which exhibits increasedsolubility in a developing solution under action of acid.

The term “base component” refers to an organic compound capable offorming a film, and is preferably an organic compound having a molecularweight of 500 or more. When the organic compound has a molecular weightof 500 or more, the film-forming ability is improved, and a resistpattern of nano level can be easily formed.

The organic compound used as the base component is broadly classifiedinto non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a “lowmolecular weight compound” refers to a non-polymer having a molecularweight in the range of 500 to less than 4,000.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. In the present description and claims, the term“resin” refers to a polymer having a molecular weight of 1,000 or more.

As the molecular weight of the polymer, the weight average molecularweight in terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

The component (A) is preferably a base component which exhibitsincreased polarity by the action of acid (hereafter, referred to as“component (A0)”).

In the present invention, when the component (A0) is used, since thepolarity of the component (A0) changes at unexposed portions before andafter the baking in the step (3), an excellent development contrast canbe obtained by an alkali development.

The component (A0) may be a resin component that exhibits increasedpolarity under the action of acid, a low molecular weight compound thatexhibits increased polarity under the action of acid, or a mixturethereof.

As the component (A0), a resin component that exhibits increasedpolarity under the action of acid is preferable, and a polymericcompound (A1) (hereafter, referred to as “component (A1)”) containing astructural unit (a1) derived from an acrylate ester which may have thehydrogen atom bonded to the carbon atom on the α-position substitutedwith a substituent and contains an acid decomposable group whichexhibits increased polarity by the action of acid is particularlydesirable.

It is preferable that the component (A1) include, in addition to thestructural unit (a1), a structural unit (a0) containing an —SO₂—containing cyclic group.

In addition to the structural unit (a1) or in addition to the structuralunit (a1) and the structural unit (a0), it is preferable that thecomponent (A1) further include a structural unit (a2) derived from anacrylate ester which may have the hydrogen atom bonded to the carbonatom on the α-position substituted with a substituent and contains alactone-containing cyclic group.

In addition to the structural unit (a1) or in addition to the structuralunit (a1) and at least one of the structural unit (a0) and thestructural unit (a2), it is preferable that the component (A1) furtherinclude a structural unit (a3) derived from an acrylate ester containinga polar group-containing aliphatic hydrocarbon group and may have thehydrogen atom bonded to the carbon atom on the α-position substitutedwith a substituent.

In the present descriptions and the claims, the expression “structuralunit derived from an acrylate ester” refers to a structural unit that isformed by the cleavage of the ethylenic double bond of an acrylateester.

An “acrylate ester” refers to a compound in which the terminal hydrogenatom of the carboxy group of acrylic acid (CH₂═CH—COOH) has beensubstituted with an organic group.

The acrylate ester may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent. The substituent thatsubstitutes the hydrogen atom bonded to the carbon atom on theα-position is atom other than hydrogen or a group, and examples thereofinclude an alkyl group of 1 to 5 carbon atoms, a halogenated alkyl groupof 1 to 5 carbon atoms and a hydroxyalkyl group. A carbon atom on theα-position of an acrylate ester refers to the carbon atom bonded to thecarbonyl group, unless specified otherwise.

Hereafter, an acrylic acid and an acrylate ester which have the hydrogenatom bonded to the carbon atom on the α-position substituted with asubstituent is sometimes referred to as “α-substituted acrylic acid” and“α-substituted acrylate ester”, respectively.

Further, the acrylic acid and α-substituted acrylic acids arecollectively referred to as “(α-substituted) acrylic acid”, and acrylateesters and α-substituted acrylate esters are collectively referred to as“(α-substituted) acrylate ester”.

In the α-substituted acrylate ester, the alkyl group as the substituenton the α-position is preferably a linear or branched alkyl group, andspecific examples thereof include a methyl group, an ethyl group, apropyl group, an isopropyl group, an n-butyl group, an isobutyl group, atert-butyl group, a pentyl group, an isopentyl group and a neopentylgroup.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsas the substituent on the α-position include groups in which part or allof the hydrogen atoms of the aforementioned “alkyl group of 1 to 5carbon atoms as the substituent on the α-position” are substituted withhalogen atoms. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

It is preferable that a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms is bonded tothe α-position of the α-substituted acrylate ester, a hydrogen atom, analkyl group of 1 to 5 carbon atoms or a fluorinated alkyl group of 1 to5 carbon atoms is more preferable, and in terms of industrialavailability, a hydrogen atom or a methyl group is the most desirable.

[Structural Unit (a1)]

The structural unit (a1) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains an aciddecomposable group which exhibits increased polarity by the action ofacid.

The term “acid decomposable group” refers to a group in which at least apart of the bond within the structure thereof is cleaved by the actionof an acid.

Examples of acid decomposable groups which exhibit increased polarity bythe action of an acid include groups which are decomposed by the actionof an acid to form a polar group.

Examples of the polar group include a carboxy group, a hydroxy group, anamino group and a sulfo group (—SO₃H). Among these, a polar groupcontaining —OH in the structure thereof (hereafter, referred to as“OH-containing polar group”) is preferable, a carboxy group or a hydroxygroup is more preferable, and a carboxy group is particularly desirable.

More specifically, as an example of an acid decomposable group, a groupin which the aforementioned polar group has been protected with an aciddissociable group (such as a group in which the hydrogen atom of theOH-containing polar group has been protected with an acid dissociablegroup) can be given.

An “acid dissociable group” is a group in which at least the bondbetween the acid dissociable group and the adjacent carbon atom iscleaved by the action of acid. It is necessary that the acid dissociablegroup that constitutes the acid decomposable group is a group whichexhibits a lower polarity than the polar group generated by thedissociation of the acid dissociable group. Thus, when the aciddissociable group is dissociated by the action of acid, a polar groupexhibiting a higher polarity than that of the acid dissociable group isgenerated, thereby increasing the polarity. As a result, the polarity ofthe entire component (A1) is increased. By the increase in the polarity,the solubility in an alkali developing solution changes and, thesolubility in an alkali developing solution is relatively increased.

The acid dissociable group is not particularly limited, and any of thegroups that have been conventionally proposed as acid dissociable groupsfor the base resins of chemically amplified resists can be used.Generally, groups that form either a cyclic or chain-like tertiary alkylester with the carboxyl group of the (meth)acrylic acid, and acetal-typeacid dissociable groups such as alkoxyalkyl groups are widely known.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(═O)—O—). Inthis tertiary alkyl ester, the action of acid causes cleavage of thebond between the oxygen atom and the tertiary carbon atom, therebyforming a carboxy group.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable groups”.

Examples of tertiary alkyl ester-type acid dissociable groups includealiphatic branched, acid dissociable groups and aliphatic cyclicgroup-containing acid dissociable groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable group” is notlimited to be constituted of only carbon atoms and hydrogen atoms (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

As an example of the aliphatic branched, acid dissociable group, forexample, a group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) can begiven (in the formula, each of R⁷¹ to R⁷³ independently represents alinear alkyl group of 1 to 5 carbon atoms). The group represented by theformula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4 to 8 carbon atoms, andspecific examples include a tert-butyl group, a 2-methyl-2-butyl group,a 2-methyl-2-pentyl group and a 3-methyl-3-pentyl group.

Among these, a tert-butyl group is particularly desirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

In the “aliphatic cyclic group-containing acid dissociable group”, the“aliphatic cyclic group” may or may not have a substituent. Examples ofthe substituent include an alkyl group of 1 to 5 carbon atoms, an alkoxygroup of 1 to 5 carbon atoms, a fluorine atom, a fluorinated alkyl groupof 1 to 5 carbon atoms, and an oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with an alkyl group of 1 to 5 carbon atoms, afluorine atom or a fluorinated alkyl group, may be used. Specificexamples of aliphatic cyclic hydrocarbon groups include groups in whichone or more hydrogen atoms have been removed from a monocycloalkane suchas cyclopentane or cyclohexane; and groups in which one or more hydrogenatoms have been removed from a polycycloalkane such as adamantane,norbornane, isobornane, tricyclodecane or tetracyclododecane. In thesealiphatic cyclic hydrocarbon groups, part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Examples of aliphatic cyclic group-containing acid dissociable groupsinclude

(i) a monovalent aliphatic cyclic group in which a substituent (a groupor an atom other than hydrogen) is bonded to the carbon atom on the ringskeleton to which an atom adjacent to the acid dissociable group (e.g.,“—O—” within “—C(═O)—O— group”) is bonded to form a tertiary carbonatom; and

(ii) a group which has a branched alkylene group containing a tertiarycarbon atom, and a monovalent aliphatic cyclic group to which thetertiary carbon atom is bonded.

In the group (i), as the substituent bonded to the carbon atom to whichan atom adjacent to the acid dissociable group on the ring skeleton ofthe aliphatic cyclic group, an alkyl group can be mentioned. Examples ofthe alkyl group include the same groups as those represented by R¹⁴ informulae (1-1) to (1-9) described later.

Specific examples of the group (i) include groups represented by generalformulae (1-1) to (1-9) shown below.

Specific examples of the group (ii) include groups represented bygeneral formulae (2-1) to (2-6) shown below.

In the formulae above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formula above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

In formulae (1-1) to (1-9), the alkyl group for R¹⁴ may be linear,branched or cyclic, and is preferably linear or branched.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

In formulae (2-1) to (2-6), as the alkyl group for R¹⁵ and R¹⁶, the samealkyl groups as those for R¹⁴ can be used.

In formulae (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulae (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of the substituent includean alkyl group of 1 to 5 carbon atoms, a fluorine atom and a fluorinatedalkyl group.

An “acetal-type acid dissociable group” generally substitutes a hydrogenatom at the terminal of an OH-containing polar group such as a carboxygroup or hydroxyl group, so as to be bonded with an oxygen atom. Whenacid acts to break the bond between the acetal-type acid dissociablegroup and the oxygen atom to which the acetal-type, acid dissociablegroup is bonded, an OH-containing polar group such as a carboxy group ora hydroxy group is formed.

Examples of acetal-type acid dissociable groups include groupsrepresented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor an alkyl group of 1 to 5 carbon atoms; n represents an integer of 0to 3; and Y represents an alkyl group of 1 to 5 carbon atoms or analiphatic cyclic group.

In general formula (p1), n is preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 0.

As the lower alkyl group for R¹′ and R²′, the same lower alkyl groups asthose described above the alkyl groups as the substituent which may bebonded to the carbon atom on the α-position of the aforementionedα-substituted alkylester can be used, although a methyl group or ethylgroup is preferable, and a methyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable group (p1) is a group represented by general formula (p1-1)shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the alkyl group for Y, the same alkyl groups as those described abovethe for the substituent which may be bonded to the carbon atom on theα-position of the aforementioned α-substituted alkylester can bementioned.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same aliphatic cyclic groups described above in connectionwith the “acid dissociable group containing an aliphatic cyclic group”can be used.

Further, as the acetal-type, acid dissociable group, groups representedby general formula (p2) shown below can also be used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the terminal of R¹⁷is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be ahydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ormethyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto. Such a cyclic group is preferably a 4- to7-membered ring, and more preferably a 4- to 6-membered ring. Specificexamples of the cyclic group include tetrahydropyranyl group andtetrahydrofuranyl group.

Examples of the structural unit (a1) include a structural unit derivedfrom an acrylate ester in which the hydrogen atom bonded to the carbonatom on the α-position may be substituted with a substituent andcontaining an acid-decomposable group that exhibits increased polarityunder the action of acid; a structural unit derived from hydroxystyreneor a hydroxystyrene derivative in which at least part of the hydroxylgroup hydrogen atoms are protected with a substituent containing anacid-decomposable group; and a structural unit derived from vinylbenzoicacid or a vinylbenzoic acid derivative in which at least part of thehydrogen atoms in the —C(═O)—OH moiety within the structural unit areprotected with a substituent containing an acid-decomposable group.Preferable examples of the substituent containing an acid-decomposablegroup include the tertiary alkyl ester-type acid-dissociable groups andacetal-type acid-dissociable groups described above.

In the present descriptions and the claims, a “structural unit derivedfrom hydroxystyrene or a hydroxystyrene derivative” refers to astructural unit that is formed by the cleavage of the ethylenic doublebond of hydroxystyrene or a hydroxystyrene derivative.

The expression “hydroxystyrene derivative” is a generic term thatincludes compounds in which the hydrogen atom on the α-position ofhydroxystyrene has been substituted with a substituent such as an alkylgroup or a halogenated alkyl group, and derivatives thereof. Unlessspecified otherwise, “the α-position” (“carbon atom on the α-position”)refers to the carbon atom to which the benzene group is bonded.

A “structural unit derived from vinylbenzoic acid or a vinylbenzoic acidderivative” refers to a structural unit that is formed by the cleavageof the ethylenic double bond of vinylbenzoic acid or a vinylbenzoic acidderivative.

The expression “vinylbenzoic acid derivative” is a generic term thatincludes compounds in which the hydrogen atom on the α-position ofvinylbenzoic acid has been substituted with a substituent such as analkyl group or a halogenated alkyl group, and derivatives thereof.Unless specified otherwise, “the α-position” (“carbon atom on theα-position”) refers to the carbon atom to which the benzene group isbonded.

Among these, the structural unit (a1) is preferably a structural unitderived from an acrylate ester in which the hydrogen atom bonded to thecarbon atom on the α-position may be substituted with a substituent.

Specific examples of the structural unit (a1) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X¹represents an acid dissociable group; Y² represents a divalent linkinggroup; and X² represents an acid dissociable group.

In general formula (a1-0-1), the alkyl group and the halogenated alkylgroup for R are respectively the same as defined for the alkyl group andthe halogenated alkyl group for the substituent which may be bonded tothe carbon atom on the α-position of the aforementioned α-substitutedacrylate ester. R is preferably a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a fluorinated alkyl group of 1 to 5 carbon atoms, andmost preferably a hydrogen atom or a methyl group.

X¹ is not particularly limited as long as it is an acid dissociablegroup. Examples thereof include the aforementioned tertiary alkylester-type acid dissociable groups and acetal-type acid dissociablegroups, and tertiary alkyl ester-type acid dissociable groups arepreferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

The divalent linking group for Y² is not particularly limited, andpreferable examples thereof include a divalent hydrocarbon group whichmay have a substituent and a divalent linking group containing a heteroatom.

A hydrocarbon “has a substituent” means that part or all of the hydrogenatoms within the hydrocarbon group is substituted with a substituent (agroup or an atom other than hydrogen).

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group.

An “aliphatic hydrocarbon group” refers to a hydrocarbon group that hasno aromaticity.

The divalent aliphatic hydrocarbon group as the divalent hydrocarbongroup for Y² may be either saturated or unsaturated. In general, thedivalent aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4,and most preferably 1 to 3.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structurethereof, an alicyclic hydrocarbon group (a group in which two hydrogenatoms have been removed from an aliphatic hydrocarbon ring), a group inwhich the alicyclic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group, and a group inwhich the alicyclic group is interposed within the aforementioned linearor branched aliphatic hydrocarbon group, can be given. As the linear orbranched aliphatic hydrocarbon group, the same groups as those describedabove can be used.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic aliphatic hydrocarbon group, a groupin which 2 hydrogen atoms have been removed from a monocycloalkane ispreferable. The monocycloalkane preferably has 3 to 6 carbon atoms, andspecific examples thereof include cyclopentane and cyclohexane. As thepolycyclic group, a group in which two hydrogen atoms have been removedfrom a polycycloalkane is preferable, and the polycyclic grouppreferably has 7 to 12 carbon atoms. Examples of the polycycloalkaneinclude adamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The alicyclic hydrocarbon group may or may not have a substituent.Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring.

The aromatic hydrocarbon group as the divalent hydrocarbon group for Y²preferably has 5 to 30 carbon atoms, more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 10. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Examples of the aromatic ring contained in the aromatic hydrocarbongroup include aromatic hydrocarbon rings, such as benzene, biphenyl,fluorene, naphthalene, anthracene and phenanthrene; and aromatic heterorings in which part of the carbon atoms constituting the aforementionedaromatic hydrocarbon rings has been substituted with a hetero atom.Examples of the hetero atom within the aromatic hetero rings include anoxygen atom, a sulfur atom and a nitrogen atom.

Specific examples of the aromatic hydrocarbon group include a group inwhich two hydrogen atoms have been removed from the aforementionedaromatic hydrocarbon ring (arylene group); and a group in which onehydrogen atom has been removed from the aforementioned aromatichydrocarbon ring (aryl group) and one hydrogen atom has been substitutedwith an alkylene group (such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group). The alkylene group (alkyl chainwithin the arylalkyl group) preferably has 1 to 4 carbon atom, morepreferably 1 or 2, and most preferably 1.

The aromatic hydrocarbon group may or may not have a substituent. Forexample, the hydrogen atom bonded to the aromatic hydrocarbon ringwithin the aromatic hydrocarbon group may be substituted with asubstituent. Examples of substituents include an alkyl group, an alkoxygroup, a halogen atom, a halogenated alkyl group, a hydroxyl group andan oxygen atom (═O).

The alkyl group as the substituent is preferably an alkyl group of 1 to5 carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent is preferably an alkoxy group having1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

With respect to a “divalent linking group containing a hetero atom” forY², a hetero atom is an atom other than carbon and hydrogen, andexamples thereof include an oxygen atom, a nitrogen atom, a sulfur atomand a halogen atom.

Examples of the divalent linking group containing a hetero atom include—O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH—, —NH—C(═O)— (Hfor NH may be substituted with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂—, —S(═O)₂—O—, ═N—, and a group representedby general formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²— or—Y²¹—O—C(═O)—Y²²— [wherein Y²¹ and Y²² each independently represents adivalent hydrocarbon group which may have a substituent, O represents anoxygen atom, and m′ represents an integer of 0 to 3.]

When Y² represents —NH—, H may be substituted with a substituent such asan alkyl group, an acyl group or the like. The substituent (an alkylgroup, an acyl group or the like) preferably has 1 to 10 carbon atoms,more preferably 1 to 8, and most preferably 1 to 5.

In formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²— or —Y²¹—O—C(═O)—Y²²—,Y²¹ and Y²² each independently represents a divalent hydrocarbon groupwhich may have a substituent. As the divalent hydrocarbon group, thesame groups as those described above for the “divalent hydrocarbon groupwhich may have a substituent” for Y² can be mentioned.

As Y²¹, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As Y²², a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula —[Y²¹—C(═O)—O]_(m′)—Y²²—, m′represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1. Namely, it is particularlydesirable that the group represented by the formula—[Y²¹—C(═O)—O]_(m′)—Y²²— is a group represented by the formula—Y²¹—C(═O)—O—Y²²—. Among these, a group represented by the formula—(CH₂)_(a′)—C(═O)—O—(CH₂)_(b′)— is preferable. In the formula, a′ is aninteger of 1 to 10, preferably an integer of 1 to 8, more preferably aninteger of 1 to 5, still more preferably 1 or 2, and most preferably 1.b′ is an integer of 1 to 10, preferably an integer of 1 to 8, morepreferably an integer of 1 to 5, still more preferably 1 or 2, and mostpreferably 1.

As the divalent linking group containing a hetero atom, a linear groupcontaining an oxygen atom as the hetero atom e.g., a group containing anether bond or an ester bond is preferable, and a group represented bythe aforementioned formula —Y²¹—O—Y²²—, —[Y²¹—C(═O)—O]_(m′)—Y²²— or—Y²¹—O—C(═O)—Y²²— is more preferable.

Among the aforementioned examples, as the divalent linking group for Y²,an alkylene group, a divalent alicyclic hydrocarbon group or a divalentlinking group containing a hetero atom is particularly desirable. Amongthese, an alkylene group or a divalent linking group containing a heteroatom is more preferable.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulae (a1-1) to (a1-4) shown below.

In the formulae, R, R¹′, R²′, n, Y and Y² are the same as defined above;and X′ represents a tertiary alkyl ester-type acid dissociable group.

In the formulae, the tertiary alkyl ester-type acid dissociable groupfor X′ include the same tertiary alkyl ester-type acid dissociablegroups as those described above.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′,n and Y in general formula (p1) described above in connection with the“acetal-type acid dissociable group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

In the present invention, as the structural unit (a1), it is preferableto include at least one structural unit selected from the groupconsisting of a structural unit represented by general formula (a1-0-11)shown below, a structural unit represented by general formula (a1-0-12)shown below, a structural unit represented by general formula (a1-0-13)shown below, a structural unit represented by general formula (a1-0-14)shown below, a structural unit represented by general formula (a1-0-15)shown below and a structural unit represented by general formula(a1-0-2) shown below.

Among these examples, as the structural unit (a1), it is preferable toinclude at least one structural unit selected from the group consistingof a structural unit represented by general formula (a1-0-11) shownbelow, a structural unit represented by general formula (a1-0-12) shownbelow, a structural unit represented by general formula (a1-0-13) shownbelow, a structural unit represented by general formula (a1-0-14) shownbelow and a structural unit represented by general formula (a1-0-15)shown below.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²¹represents an alkyl group; R²² represents a group which forms analiphatic monocyclic group with the carbon atom to which R²² is bonded;R²³ represents a branched alkyl group; R²⁴ represents a group whichforms an aliphatic polycyclic group with the carbon atom to which R²⁴ isbonded; R²⁵ represents a linear alkyl group of 1 to 5 carbon atoms; R¹⁵and R¹⁶ each independently represents an alkyl group; Y² represents adivalent linking group; and X² an acid dissociable group.

In the formulae, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R²¹, the same alkylgroups as those described above for R¹⁴ in formulae (1-1) to (1-9) canbe used, preferably a methyl group, an ethyl group or an isopropylgroup.

As the aliphatic monocyclic group formed by R²² and the carbon atoms towhich R²² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociablegroup and which are monocyclic can be used. Specific examples includegroups in which one or more hydrogen atoms have been removed from amonocycloalkane. The monocycloalkane is preferably a 3-to 11-memberedring, more preferably a 3- to 8-membered ring, still more preferably a4-to 6-membered ring, and most preferably a 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ether bond (—O—).

Further, the monocycloalkane may have a substituent such as an alkylgroup of 1 to 5 carbon atoms, a fluorine atom or a fluorinated alkylgroup of 1 to 5 carbon atoms.

As an examples of R²² constituting such an aliphatic cyclic group, analkylene group which may have an ether bond (—O—) interposed between thecarbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulae (a1-1-16) to (a1-1-23), (a1-1-27) and (a1-1-31). Among these, astructural unit represented by general formula (a1-1-02) shown belowwhich includes the structural units represented by the aforementionedformulae (a1-1-16), (a1-1-17), (a1-1-20) to (a1-1-23), (a1-1-27),(a1-1-31), (a1-1-32) and (a1-1-33) is preferable. Further, a structuralunit represented by general formula (a1-1-02′) shown below is alsopreferable.

In the formulae, h represents an integer of 1 to 4, and preferably 1 or2.

In the formulae, R and R²¹ are the same as defined above; and hrepresents an integer of 1 to 4.

In general formula (a1-0-12), as the branched alkyl group for R²³, thesame alkyl groups as those described above for R¹⁴ which are branchedcan be used, and an isopropyl group is particularly desirable.

As the aliphatic polycyclic group formed by R²⁴ and the carbon atoms towhich R²⁴ is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociablegroup and which are polycyclic can be used.

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulae (a1-1-26) and (a1-1-28) to (a1-1-30).

As the structural unit (a1-0-12), a structural unit in which thealiphatic polycyclic group formed by R²⁴ and the carbon atom to whichR²⁴ is bonded is a 2-adamantyl group is preferable, and a structuralunit represented by the aforementioned formula (a1-1-26) is particularlydesirable.

In general formula (a1-0-13), R and R²⁴ are the same as defined above.

As the linear alkyl group for R²⁵, the same linear alkyl groups as thosedescribed above for R¹⁴ in the aforementioned formulae (1-1) to (1-9)can be mentioned, and a methyl group or an ethyl group is particularlydesirable.

Specific examples of structural units represented by general formula(a1-0-13) include structural units represented by the aforementionedformulae (a1-1-1), (a1-1-2) and (a1-1-7) to (a1-1-15) which weredescribed above as specific examples of the structural unit representedby general formula (a1-1).

As the structural unit (a1-0-13), a structural unit in which thealiphatic polycyclic group formed by R²⁴ and the carbon atom to whichR²⁴ is bonded is a 2-adamantyl group is preferable, and a structuralunit represented by the aforementioned formula (a1-1-1) or (a1-1-2) isparticularly desirable.

In general formula (a1-0-14), R and R²² are the same as defined above.R¹⁵ and R¹⁶ are the same as R¹⁵ and R¹⁶ in the aforementioned generalformulae (2-1) to (2-6), respectively.

Specific examples of structural units represented by general formula(a1-0-14) include structural units represented by the aforementionedformulae (a1-1-35) and (a1-1-36) which were described above as specificexamples of the structural unit represented by general formula (a1-1).

In general formula (a1-0-15), R and R²⁴ are the same as defined above.R¹⁵ and R¹⁶ are the same as R¹⁵ and R¹⁶ in the aforementioned generalformulae (2-1) to (2-6), respectively.

Specific examples of structural units represented by general formula(a1-0-15) include structural units represented by the aforementionedformulae (a1-1-4) to (a1-1-6) and (a1-1-34) which were described aboveas specific examples of the structural unit represented by generalformula (a1-1).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulae(a1-3) and (a1-4). The structural unit represented by formula (a1-3) isparticularly desirable.

As a structural unit represented by general formula (a1-0-2), those inwhich Y² is a group represented by the aforementioned formula—Y²¹—O—Y²²— or —Y²¹—C(O)—O—Y²²— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-3-01) shown below, a structural unitrepresented by general formula (a1-3-02) shown below, and a structuralunit represented by general formula (a1-3-03) shown below.

In the formulae, R is the same as defined above; R¹³ represents ahydrogen atom or a methyl group; R¹⁴ represents an alkyl group; erepresents an integer of 1 to 10; and n′ represents an integer of 0 to3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociablegroup; and w represents an integer of 0 to 3.

In general formulae (a1-3-01) and (a1-3-02), R¹³ is preferably ahydrogen atom.

R¹⁴ is the same as defined for R¹⁴ in the aforementioned formulae (1-1)to (1-9).

e is preferably an integer of 1 to 8, more preferably an integer of 1 to5, and most preferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-3-01) include structural units represented by the aforementionedformulae (a1-3-25) and (a1-3-26).

Specific examples of structural units represented by general formula(a1-3-02) include structural units represented by the aforementionedformulae (a1-3-27) and (a1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable group for X′, the same groups as those describedabove can be used. X′ is preferably a tertiary alkyl ester-type aciddissociable group, more preferably the aforementioned group (i) in whicha substituent is bonded to the carbon atom to which an atom adjacent tothe acid dissociable group is bonded to on the ring skeleton to form atertiary carbon atom. Among these, a group represented by theaforementioned general formula (1-1) is particularly desirable.

w represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) or(a1-3-03-2) shown below is preferable, and a structural unit representedby general formula (a1-3-03-1) is particularly desirable.

In the formulae, R and R¹⁴ are the same as defined above; a′ representsan integer of 1 to 10; b′ represents an integer of 1 to 10; and trepresents an integer of 0 to 3.

In general formulae (a1-3-03-1) and (a1-3-03-2), a′ is the same asdefined above, preferably an integer of 1 to 8, more preferably 1 to 5,and most preferably 1 or 2.

b′ is the same as defined above, preferably an integer of 1 to 8, morepreferably 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

Specific examples of structural units represented by general formula(a1-3-03-1) or (a1-3-03-2) include structural units represented by theaforementioned formulae (a1-3-29) to (a1-3-32).

As the structural unit (a1) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 15 to 70 mol %, more preferably 15 to 60 mol %, andstill more preferably 20 to 55 mol %.

When the amount of the structural unit (a1) is at least as large as thelower limit of the above-mentioned range, a pattern can be easily formedusing a resist composition prepared from the component (A1), and variouslithography properties such as sensitivity, resolution, LWR and the likeare improved. On the other hand, when the amount of the structural unit(a1) is no more than the upper limit of the above-mentioned range, agood balance can be reliably achieved with the other structural units.

[Structural Unit (a0)]

The structural unit (a0) is a structural unit containing an —SO₂—containing cyclic group.

By virtue of the structural unit (a0) containing a —SO₂— containingcyclic group, a resist composition containing the component (A1)including the structural unit (a0) is capable of improving the adhesionof a resist film to a substrate. Further, the structural unit (a0)contributes to improvement in various lithography properties such assensitivity, resolution, exposure latitude (EL margin), line widthroughness (LWR), line edge roughness (LER) and mask reproducibility.

Here, an “—SO₂— containing cyclic group” refers to a cyclic group havinga ring containing —SO₂— within the ring structure thereof, i.e., acyclic group in which the sulfur atom (S) within —SO₂— forms part of thering skeleton of the cyclic group.

In the —SO₂— containing cyclic group, the ring containing —SO₂— withinthe ring skeleton thereof is counted as the first ring. A cyclic groupin which the only ring structure is the ring that contains —SO₂— in thering skeleton thereof is referred to as a monocyclic group, and a groupcontaining other ring structures is described as a polycyclic groupregardless of the structure of the other rings.

The —SO₂— containing cyclic group may be either a monocyclic group or apolycyclic group.

As the —SO₂— containing cyclic group, a cyclic group containing —O—SO₂—within the ring skeleton thereof, i.e., a cyclic group containing asultone ring in which —O—S— within the —O—SO₂— group forms part of thering skeleton thereof is particularly desirable.

The —SO₂— containing cyclic group preferably has 3 to 30 carbon atoms,more preferably 4 to 20, still more preferably 4 to 15, and mostpreferably 4 to 12. Herein, the number of carbon atoms refers to thenumber of carbon atoms constituting the ring skeleton, excluding thenumber of carbon atoms within a substituent.

The —SO₂— containing cyclic group may be either a —SO₂— containingaliphatic cyclic group or a —SO₂— containing aromatic cyclic group. A—SO₂— containing aliphatic cyclic group is preferable.

Examples of the —SO₂— containing aliphatic cyclic group includealiphatic cyclic groups in which part of the carbon atoms constitutingthe ring skeleton has been substituted with a —SO₂— group or a —O—SO₂—group and has at least one hydrogen atom removed from the aliphatichydrocarbon ring. Specific examples include an aliphatic hydrocarbonring in which a —CH₂— group constituting the ring skeleton thereof hasbeen substituted with a —SO₂— group and has at least one hydrogen atomremoved therefrom; and an aliphatic hydrocarbon ring in which a—CH₂—CH₂— group constituting the ring skeleton has been substituted witha —O—SO₂— group and has at least one hydrogen atom removed therefrom.

The alicyclic hydrocarbon group preferably has 3 to 20 carbon atoms, andmore preferably 3 to 12 carbon atoms.

The alicyclic hydrocarbon group may be either a monocyclic group or apolycyclic group. As the monocyclic group, a group in which two hydrogenatoms have been removed from a monocycloalkane of 3 to 6 carbon atoms ispreferable. Examples of the monocycloalkane include cyclopentane andcyclohexane. As the polycyclic group, a group in which two hydrogenatoms have been removed from a polycycloalkane of 7 to 12 carbon atomsis preferable. Examples of the polycycloalkane include adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane.

The —SO₂— containing cyclic group may have a substituent. Examples ofthe substituent include an alkyl group, an alkoxy group, a halogen atom,a halogenated alkyl group, a hydroxy group, an oxygen atom (═O), —COOR″,—OC(═O)R″, a hydroxyalkyl group and a cyano group (wherein R″ representsa hydrogen atom or an alkyl group).

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

The alkoxy group for the substituent is preferably an alkoxy group of 1to 6 carbon atoms. The alkoxy group is preferably a linear or branchedgroup. Specific examples include groups in which an oxygen atom (—O—) isbonded to any of the alkyl groups described above as the substituent.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

As examples of the halogenated lower alkyl group for the substituent,groups in which part or all of the hydrogen atoms of the aforementionedalkyl groups for the substituent have been substituted with theaforementioned halogen atoms can be given. As the halogenated alkylgroup, a fluorinated alkyl group is preferable, and a perfluoroalkylgroup is particularly desirable.

In the —COOR″ group and the —OC(═O)R″ group, R″ preferably represents ahydrogen atom or a linear, branched or cyclic alkyl group of 1 to 15carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

More specific examples of the —SO₂— containing cyclic group includegroups represented by general formulae (3-1) to (3-4) shown below.

In the formulae, A′ represents an oxygen atom, a sulfur atom or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; z represents an integer of 0 to 2; and R⁶ representsan alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.

In general formulae (3-1) to (3-4) above, A′ represents an oxygen atom(—O—), a sulfur atom (—S—) or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom.

As the alkylene group of 1 to 5 carbon atoms represented by A′, a linearor branched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or present between the carbonatoms of the alkylene group. Specific examples of such alkylene groupsinclude —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, —CH₂—S—CH₂—.

As A′, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

z represents an integer of 0 to 2, and is most preferably 0.

When z is 2, the plurality of R⁶ may be the same or different from eachother.

As the alkyl group, alkoxy group, halogenated alkyl group, —COOR″,—OC(═O)R″ and hydroxyalkyl group for R⁶, the same alkyl groups, alkoxygroups, halogenated alkyl groups, —COOR″, —OC(═O)R″ and hydroxyalkylgroups as those described above as the substituent for the —SO₂—containing cyclic group can be mentioned.

Specific examples of the cyclic groups represented by general formulae(3-1) to (3-4) are shown below. In the formulae shown below, “Ac”represents an acetyl group.

Of the groups shown above, the —SO₂-containing cyclic group ispreferably a group represented by the general formula (3-1), (3-3) or(3-4), more preferably at least one group selected from the groupconsisting of groups represented by the above chemical formulas (3-1-1),(3-1-18), (3-3-1) and (3-4-1), and most preferably a group representedby the chemical formula (3-1-1).

More specifically, examples of the structural unit (a0) includestructural units represented by general formula (a0-0) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms, R³⁹represents —O— or —NH—, R³⁰ represents an —SO₂-containing cyclic group,and R²⁹′ represents a single bond or a divalent linking group.

In general formula (a0-0), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group of 1 to 5 carbon atoms for R, a linear or branchedalkyl group of 1 to 5 carbon atoms is preferable, and specific examplesthereof include a methyl group, an ethyl group, a propyl group, anisopropyl group, an n-butyl group, an isobutyl group, a tert-butylgroup, a pentyl group, an isopentyl group and a neopentyl group.

The halogenated alkyl group for R is a group in which part or all of thehydrogen atoms of the aforementioned alkyl group of 1 to 5 carbon atomshas been substituted with halogen atoms. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In formula (a0-0), R³⁹ represents —O— or —NH—.

In formula (a0-0), R³⁰ is the same as defined for the aforementioned—SO₂-containing group.

In formula (a0-0), R²⁹′ may be a single bond or a divalent linkinggroup. In terms of the effects of the present invention, lithographyproperties and the like, a divalent linking group is preferable.

As the divalent linking group for R²⁹′, for example, the same divalentlinking groups as those described for Y² in general formula (a1-0-2)explained above in relation to the structural unit (a1) can bementioned.

As the divalent linking group for R²⁹′, an alkylene group, a divalentalicyclic hydrocarbon group or a divalent linking group containing ahetero atom is preferable. Among these, an alkylene group or a divalentlinking group containing an ester bond (—C(═O)—O—) is preferable.

As the alkylene group, a linear or branched alkylene group ispreferable. Specific examples include the same linear alkylene groupsand branched alkylene groups as those described above for the aliphatichydrocarbon group represented by Y².

As the divalent linking group containing an ester bond, a grouprepresented by general formula: —R²⁰—C(═O)—O— (in the formula, R²⁰represents a divalent linking group) is particularly desirable. Namely,the structural unit (a0) is preferably a structural unit represented bygeneral formula (a0-0-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms, R³⁹represents —O— or —NH—, R²⁰ represents a divalent linking group, and R³⁰represents an —SO₂-containing cyclic group.

R²⁰ is not particularly limited. For example, the same divalent linkinggroups as those described for R²⁹′ in general formula (a0-0) can bementioned.

As the divalent linking group for R²⁰, an alkylene group, a divalentalicyclic hydrocarbon group or a divalent linking group containing ahetero atom is preferable.

As the linear or branched alkylene group, the divalent alicyclichydrocarbon group and the divalent linking group containing a heteroatom, the same linear or branched alkylene group, divalent alicyclichydrocarbon group and divalent linking group containing a hetero atom asthose described above as preferable examples of R²⁹′ can be mentioned.

Among these, a linear or branched alkylene group, or a divalent linkinggroup containing an oxygen atom as a hetero atom is more preferable.

As the linear alkylene group, a methylene group or an ethylene group ispreferable, and a methylene group is particularly desirable.

As the branched alkylene group, an alkylmethylene group or analkylethylene group is preferable, and —CH(CH₃)—, —C(CH₃)₂— or—C(CH₃)₂CH₂— is particularly desirable.

As the divalent linking group containing a hetero atom, a divalentlinking group containing an ether bond or an ester bond is preferable,and a group represented by the aforementioned formula —Y²¹—O—Y²²—,—[Y²¹—C(═O)—O]_(m′)—Y²²— or —Y²¹—O—C(═O)—Y²²— is more preferable. Y²¹,Y²² and m′ are the same as defined above.

Among these, a group represented by the formula —Y²¹—O—C(═O)—Y²²—, and agroup represented by the formula —(CH₂)_(c)—O—C(═O)—(CH₂)_(d)— isparticularly desirable. c represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2. d represents an integerof 1 to 5, preferably an integer of 1 to 3, and more preferably 1 or 2.

In particular, as the structural unit (a0), a structural unitrepresented by general formula (a0-0-11) or (a0-0-12) shown below ispreferable, and a structural unit represented by general formula(a0-0-12) is more preferable.

In the formulae, R, A′, R⁶, z, R³⁹ and R²⁰ are the same as definedabove.

In general formula (a0-0-11), A′ is preferably a methylene group, anethylene group, an oxygen atom (—O—) or a sulfur atom (—S—).

In general formula (a0-0-12), R²⁰ is preferably a linear or branchedalkylene group or a divalent linking group containing an oxygen atom. Asthe linear or branched alkylene group and the divalent linking groupcontaining an oxygen atom represented by R²⁰, the same linear orbranched alkylene groups and the divalent linking groups containing anoxygen atom as those described above can be mentioned.

As the structural unit represented by general formula (a0-0-12), astructural unit represented by general formula (a0-0-12a) or (a0-0-12b)shown below is particularly desirable.

In the formulae, R, R³⁹ and A′ are the same as defined above; c and fare the same as defined above; and f represents an integer of 1 to 5(preferably an integer of 1 to 3).

As the structural unit (a0) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

In terms of achieving an excellent shape for a resist pattern formedusing a positive resist composition containing the component (A1) andexcellent lithography properties such as EL margin, LWR and maskreproducibility, the amount of the structural unit (a0) within thecomponent (A1), based on the combined total of all structural unitsconstituting the component (A1) is preferably 1 to 60 mol %, morepreferably 5 to 55 mol %, still more preferably 10 to 50 mol %, and mostpreferably 15 to 45 mol %.

[Structural Unit (a2)]

The structural unit (a2) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains alactone-containing cyclic group.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(═O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andincreasing the compatibility with the developing solution containingwater (especially in an alkali developing process).

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include groupsin which one hydrogen atom has been removed from a 4- to 6-memberedlactone ring, including a group in which one hydrogen atom has beenremoved from β-propiolactone, a group in which one hydrogen atom hasbeen removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulae (a2-1) to (a2-5) shownbelow.

In the formulae, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; eachR′ independently represents a hydrogen atom, an alkyl group, an alkoxygroup, a halogen atom, a halogenated alkyl group, a hydroxy group, anoxygen atom (═O), —COOR″—OC(═O)R″, a hydroxyalkyl group or a cyanogroup, wherein R″ represents a hydrogen atom or an alkyl group; R²⁹represents a single bond or a divalent linking group; s″ represents aninteger of 0 or 1 to 2; A″ represents an oxygen atom, a sulfur atom oran alkylene group of 1 to 5 carbon atoms which may contain an oxygenatom or a sulfur atom; and m represents 0 or 1.

In general formulae (a2-1) to (a2-5), R is the same as defined for R inthe structural unit (a1).

As the alkyl group, alkoxy group, halogen atom, halogenated alkyl group,—COOR″, —OC(═O)R″ and hydroxyalkyl group for R′, the same alkyl groups,alkoxy groups, halogen atoms, halogenated alkyl groups, —COOR″,—OC(═O)R″(R″ is the same as defined above) and hydroxyalkyl groups asthose described above as the substituent for the —SO₂— containing cyclicgroup can be mentioned.

As A″, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

R²⁹ represents a single bond or a divalent linking group. Examples ofdivalent linking groups include the same divalent linking groups asthose described above for Y² in general formula (a1-0-2). Among these,an alkylene group, an ester bond (—C(═O)—O—) or a combination thereof ispreferable. The alkylene group as a divalent linking group for R²⁹ ispreferably a linear or branched alkylene group. Specific examplesinclude the same linear alkylene groups and branched alkylene groups asthose described above for the aliphatic hydrocarbon group represented byY².

s″ is preferably 1 or 2.

Specific examples of structural units represented by general formulae(a2-1) to (a2-5) are shown below.

In the formulae shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a2) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

As the structural unit (a2), at least one structural unit selected fromthe group consisting of formulae (a2-1) to (a2-5) is preferable, and atleast one structural unit selected from the group consisting of formulae(a2-1) to (a2-3) is more preferable. Of these, it is preferable to useat least one structural unit selected from the group consisting ofstructural units represented by formulae (a2-1-1), (a2-1-2), (a2-2-1),(a2-2-7), (a2-3-1) and (a2-3-5).

In the component (A1), the amount of the structural unit (a2) based onthe combined total of all structural units constituting the component(A1) is preferably 5 to 60 mol %, more preferably 10 to 55 mol %, stillmore preferably 10 to 50 mol %, and most preferably 10 to 45 mol %.

When the amount of the structural unit (a2) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a2) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a2) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

[Structural Unit (a3)]

The structural unit (a3) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains a polargroup-containing aliphatic hydrocarbon group (provided that theaforementioned structural units (a1), (a0) and (a2) are excluded fromthe structural unit (a3)).

When the component (A1) includes the structural unit (a3), thehydrophilicity of the component (A1) is enhanced, thereby contributingto improvement in resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which part of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulae (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulae, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.

j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3) contained in the component (A1), 1 type ofstructural unit may be used, or 2 or more types may be used.

The amount of the structural unit (a3) within the component (A1) basedon the combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %.

When the amount of the structural unit (a3) is at least as large as thelower limit of the above-mentioned range, the effect of using thestructural unit (a3) can be satisfactorily achieved. On the other hand,when the amount of the structural unit (a3) is no more than the upperlimit of the above-mentioned range, a good balance can be achieved withthe other structural units.

[Other Structural Unit]

The component (A1) may also have a structural unit other than theabove-mentioned structural units (a1), (a0), (a2) and (a3), as long asthe effects of the present invention are not impaired.

As such a structural unit, any other structural unit which cannot beclassified as the aforementioned structural units can be used withoutany particular limitation, and any of the multitude of conventionalstructural units used within resist resins for ArF excimer lasers or KrFexcimer lasers (and particularly for ArF excimer lasers) can be used.

Examples of the other structural unit include a structural unit (a4)derived from an acrylate ester which may have the hydrogen atom bondedto the carbon atom on the α-position substituted with a substituent andcontains an acid non-dissociable aliphatic polycyclic group, astructural unit (a5) derived from hydroxystyrene and a structural unit(a6) derived from styrene.

A “structural unit derived from a hydroxystyrene” refers to a structuralunit that is formed by the cleavage of the ethylenic double bond of ahydroxystyrene.

The term “hydroxystyrene” is a generic term that includes hydroxystyrenehaving a hydrogen atom bonded to the carbon atom on the α-position (thecarbon atom to which the phenyl group is bonded), hydroxystyrene havinga substituent (an atom other than a hydrogen atom or a group) bonded tothe carbon atom on the α-position, and derivatives thereof.Specifically, at least the benzene ring and the hydroxy group bonded tothe benzene ring are maintained, and examples thereof include those inwhich the hydrogen atom bonded to the α-position of hydroxystyrene hasbeen substituted with an alkyl group of 1 to 5 carbon atoms, ahalogenated alkyl group of 1 to 5 carbon atoms, a hydroxyalkyl group orthe like, and those in which the benzene ring having a hydroxy groupbonded thereto further has an alkyl group of 1 to 5 carbon atoms, orthose in which the benzene ring having a hydroxy group bonded theretofurther has one or two hydroxy groups (the total number of hydroxygroups being two or three).

A “structural unit derived from styrene” refers to a structural unitthat is formed by the cleavage of the ethylenic double bond of styrene.

The term “styrene” includes styrene, compounds in which the hydrogenatom at the α-position has been substituted with a substituent (an atomother than hydrogen or a group), and derivatives thereof (provided thatthe aforementioned hydroxystyrene is excluded). Further, those in whicha hydrogen atom of the phenyl group has been substituted with asubstituent such as an alkyl group of 1 to 5 carbon atoms are alsoincluded.

In the aforementioned hydroxystyrene or styrene, the alkyl group as thesubstituent on the α-position is preferably a linear or branched alkylgroup, and specific examples thereof include a methyl group, an ethylgroup, a propyl group, an isopropyl group, an n-butyl group, an isobutylgroup, a tert-butyl group, a pentyl group, an isopentyl group and aneopentyl group.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsas the substituent on the α-position include groups in which part or allof the hydrogen atoms of the aforementioned “alkyl group of 1 to 5carbon atoms as the substituent on the α-position” are substituted withhalogen atoms. Examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom isparticularly desirable.

Specific examples of the hydroxyalkyl group of 1 to 5 carbon atoms asthe substituent on the α-position include groups in which part or all ofthe hydrogen atoms of the aforementioned “alkyl group of 1 to 5 carbonatoms as the substituent on the α-position” are substituted with ahydroxy group. The number of hydroxy groups within the hydroxyalkylgroup is preferably 1 to 5, and most preferably 1.

(Structural Unit (a4))

The structural unit (a4) is a structural unit derived from an acrylateester which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent and contains an acidnon-dissociable aliphatic polycyclic group.

In the structural unit (a4), examples of this polycyclic group includethe same polycyclic groups as those described above in relation to theaforementioned structural unit (a1), and any of the multitude ofconventional polycyclic groups used within the resin component of resistcompositions for ArF excimer lasers or KrF excimer lasers (andparticularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecyl group, adamantylgroup, tetracyclododecyl group, isobornyl group, and norbornyl group isparticularly desirable. These polycyclic groups may be substituted witha linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulae (a4-1) to (a4-5) shown below.

In the formulae, R is the same as defined above.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

(Structural Unit (a5))

As the structural unit (a5), a structural unit represented by generalformula (a5-1) shown below is preferable because the solubility in anorganic solvent becomes excellent, the solubility in an alkalideveloping solution is increased, and the etching resistance becomesexcellent.

In the formula, R⁶⁰ represents a hydrogen atom or an alkyl group of 1 to5 carbon atoms; R⁶¹ represents an alkyl group of 1 to 5 carbon atoms; prepresents an integer of 1 to 3; and q represents an integer of 0 to 2.

In the formula (a5-1), specific examples of the alkyl group of 1 to 5carbon atoms for R⁶⁰ include linear or branched alkyl groups such as amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group. As R⁶⁰, a hydrogen atom or amethyl group is preferable.

p represents an integer of 1 to 3, and is preferably 1.

The bonding position of the hydroxy group may be any of the α-position,m-position and p-position of the phenyl group. When p is 1, thep-position is preferable in terms of availability and low cost. When pis 2 or 3, a desired combination of the bonding positions can be used.

q represents an integer of 0 to 2. q is preferably 0 or 1, and mostpreferably 0 from industrial viewpoint.

As the alkyl group for R⁶¹, the same alkyl groups as those for R⁶⁰ canbe mentioned.

When q is 1, the bonding position of R⁶¹ may be any of the o-position,the m-position and the p-position.

When q is 2, a desired combination of the bonding positions can be used.Here, the plurality of the R⁶¹ group may be the same or different fromeach other.

When the structural unit (a5) is included in the component (A1), theamount of the structural unit (a5) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 50 to 90 mol %, more preferably from 55 to 85 mol%, and still more preferably 60 to 80 mol %.

(Structural Unit (a6))

As the structural unit (a6), a structural unit represented by generalformula (a6-1) shown below is preferable because the solubility in analkali developing solution can be adjusted, and heat resistance and dryetching resistance are improved.

In the formula, R⁶⁰ represents a hydrogen atom or an alkyl group of 1 to5 carbon atoms; R⁶² represents an alkyl group of 1 to 5 carbon atoms;and x represents an integer of 0 to 3.

In general formula (a6-1), R⁶⁰ is the same as defined above for R⁶⁰ inthe aforementioned general formula (a5-1).

In the formula (a6-1), as the alkyl group for R⁶², the same alkyl groupsas those for R⁶¹ in the aforementioned formula (a5-1) can be mentioned.

x represents an integer of 0 to 3, preferably 0 or 1, and mostpreferably 0 in terms of industry.

When x represents 1, the substitution position of R⁶² may be any ofo-position, m-position or p-position of the phenyl group. When x is 2 or3, a desired combination of the bonding positions can be used. Here, theplurality of the R⁶² group may be the same or different from each other.

When the structural unit (a6) is included in the component (A1), theamount of the structural unit (a6) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 10 to 50 mol %, more preferably from 15 to 45 mol%, and still more preferably 20 to 40 mol %.

In the resist composition of the present invention, the component (A)preferably contains a polymeric compound (A1) having a structural unit(a1).

Specific examples of the component (A1) include a polymeric compoundconsisting of the repeated structure of a structural unit (a1) and astructural unit (a2); a polymeric compound consisting of the repeatedstructure of a structural unit (a1) and a structural unit (a0); apolymeric compound consisting of the repeated structure of a structuralunit (a1), a structural unit (a2) and a structural unit (a3); apolymeric compound consisting of the repeated structure of a structuralunit (a1), a structural unit (a0) and a structural unit (a3); and apolymeric compound consisting of the repeated structure of a structuralunit (a1), a structural unit (a0), a structural unit (a2) and astructural unit (a3).

Among these, preferable examples of the component (A1) include apolymeric compound consisting of structural units (a1), (a2) and (a3);and a polymeric compound consisting of structural units (a1), (a0), (a2)and (a3).

More specifically, preferable examples thereof include a polymericcompound having the combination of the structural unit represented bythe aforementioned formula (a1-0-12) or (a1-0-13), the structural unitrepresented by the aforementioned formula (a2-1) and the structural unitrepresented by the aforementioned formula (a3-1), and a polymericcompound having the combination of the structural unit represented bythe aforementioned formula (a1-0-11), the structural unit represented bythe aforementioned formula (a1-0-12), the structural unit represented bythe aforementioned formula (a0-0-12), the structural unit represented bythe aforementioned formula (a2-1) and the structural unit represented bythe aforementioned formula (a3-1).

A polymeric compound having the combination of the structural unitrepresented by the aforementioned formula (a1-1-1) or (a1-1-26), thestructural unit represented by the aforementioned formula (a2-1-1) andthe structural unit represented by the aforementioned formula (a3-1), ora polymeric compound having the combination of the structural unitrepresented by the aforementioned formula (a1-1-26), the structural unitrepresented by the aforementioned formula (a1-1-20), the structural unitrepresented by the aforementioned formula (a0-0-12a), the structuralunit represented by the aforementioned formula (a2-1-1) and thestructural unit represented by the aforementioned formula (a3-1) isparticularly desirable.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A1)is not particularly limited, but is preferably 1,000 to 50,000, morepreferably 1,500 to 30,000, and most preferably 2,000 to 20,000. Whenthe weight average molecular weight is no more than the upper limit ofthe above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is not particularly limited, but ispreferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably1.0 to 2.5. Here, Mn is the number average molecular weight.

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

In the component (A), as the component (A1), one type may be used alone,or two or more types may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, various lithography propertiesare improved, such as improvement in MEF and circularity, and reductionof roughness.

The component (A) may contain “a base component which exhibits increasedpolarity under action of acid” other than the component (A1) (hereafter,referred to as “component (A2)”), as long as the effects of the presentinvention are not impaired.

Examples of the component (A2) include low molecular weight compoundsthat have a molecular weight of at least 500 and less than 4,000,contains a hydrophilic group, and also contains an acid dissociablegroup described above in connection with the component (A1). Thecomponent (A2) preferably has a molecular weight of at least 500 andless than 2,500. Specific examples include compounds containing aplurality of phenol skeletons in which part or all of the hydrogen atomswithin hydroxyl groups have been substituted with the aforementionedacid dissociable groups.

Examples of the low-molecular weight compound include low molecularweight phenolic compounds in which a portion of the hydroxyl grouphydrogen atoms have been substituted with an aforementioned aciddissociable group, and these types of compounds are known, for example,as sensitizers or heat resistance improvers for use in non-chemicallyamplified g-line or i-line resists.

Examples of these low molecular weight phenol compounds includebis(4-hydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane,2-(4-hydroxyphenyl)-2-(4′-hydroxyphenyl)propane,2-(2,3,4-trihydroxyphenyl)-2-(2′,3′,4′-trihydroxyphenyl)propane,tris(4-hydroxyphenyl)methane,bis(4-hydroxy-3,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-3,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-3-methylphenyl)-3,4-dihydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-4-hydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-3,4-dihydroxyphenylmethane,1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene,and dimers, trimers, tetramers, pentamers and hexamers of formalincondensation products of phenols such as phenol, m-cresol, p-cresol andxylenol. Needless to say, the low molecular weight phenol compound isnot limited to these examples. In particular, a phenol compound having 2to 6 triphenylmethane skeletons is preferable in terms of resolution andline width roughness (LER). Also, there are no particular limitations onthe acid dissociable group, and suitable examples include the groupsdescribed above.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

Photo-Base Generator Component; Component (C)

In the method of forming a resist pattern of the present invention, byvirtue of the component (C) being decomposed in step (2) by the exposureenergy to generate a base, an excellent dissolution contrast can beobtained.

The component (C) may be any compound capable of being decomposed byirradiation of radiation to generate a base, and examples thereofinclude a compound containing a carbamate group (a urethane bond), acompound containing an acyloxyimino group, an ionic compound (ananion-cation complex), and a compound containing a carbamoyloxyiminogroup. Among these, a compound containing a carbamate group (a urethanebond), a compound containing an acyloxyimino group, and an ioniccompound (an anion-cation complex) are preferable.

Further, compounds having a ring structure within a molecule thereof arepreferable, and examples thereof include compounds having a ringskeleton such as benzene, naphthalene, anthracene, xanthone,thioxanthone, anthraquinone or fluorene.

Among these, as the component (C), in terms of photodegradability, acompound represented by general formula (C1) shown below (hereafter,referred to as “component (C1)”) is particularly desirable. When thecompound is irradiated by radiation, at least the bond between thenitrogen atom in the formula (C1) and the carbon atom of the carbonylgroup adjacent to the nitrogen atom is cleaved, thereby generating anamine or ammonia and carbon dioxide. At this time, after thedecomposition, since the product contains —N(R¹)(R²), which has a highboiling point, the product can be prevented from vaporizing by thebaking (PEB) in the step (3). Accordingly, since the degree of freedomin selecting the baking temperature is enhanced, it is preferable thatthe product containing —N(R¹)(R²) have a high boiling point. Further, interms of suppressing diffusion of a base during PEB, it is preferablethat the product containing —N(R¹)(R²) has a large molecular weight or ahighly bulky skeleton.

In the formula, R¹ and R² each independently represents a hydrogen atomor a monovalent hydrocarbon group which may contain a hetero atom,provided that R¹ and R² may be mutually bonded to form a cyclic groupwith the adjacent nitrogen atom; and R³ represents a monovalentphotoactive group.

In formula (C1), the hetero atom which may be contained in thehydrocarbon group for R¹ and R² is an atom other than hydrogen andcarbon, and examples thereof include an oxygen atom, a nitrogen atom, asulfur atom and a halogen atom. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom.

The hydrocarbon group may be either an aromatic hydrocarbon group or analiphatic hydrocarbon group, and is preferably an aliphatic hydrocarbongroup.

In formula (C1), the aromatic hydrocarbon group for R¹ and R² is ahydrocarbon group having an aromatic ring.

The aromatic hydrocarbon group for R¹ and R² preferably has 5 to 30carbon atoms, more preferably 5 to 20, still more preferably 6 to 15,and most preferably 6 to 12. Here, the number of carbon atoms within asubstituent(s) is not included in the number of carbon atoms of thearomatic hydrocarbon group.

Specific examples of the aromatic hydrocarbon group include an arylgroup which is an aromatic hydrocarbon ring having one hydrogen atomremoved therefrom, such as a phenyl group, a biphenyl group, a fluorenylgroup, a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

Further, when the aromatic hydrocarbon group has an aliphatichydrocarbon group bonded to the aromatic ring, part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with adivalent linking group containing a hetero atom, or part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group. As examples of the “aliphatichydrocarbon group” and the “divalent linking group containing a heteroatom”, the same aliphatic hydrocarbon groups and divalent linking groupscontaining a hetero atom as those described later for R¹ and R² can bementioned.

Examples of the aromatic hydrocarbon group in which part of the carbonatoms constituting the aromatic ring has been substituted with a heteroatom include a heteroaryl group in which part of the carbon atomsconstituting the ring within the aforementioned aryl group has beensubstituted with a hetero atom such as an oxygen atom, a sulfur atom ora nitrogen atom, and a heteroarylalkyl group in which part of the carbonatoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom.

Examples of the substituent group which substitutes the hydrogen atombonded to the aromatic ring of the aforementioned aromatic hydrocarbongroup include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxyalkyl group, a hydroxy group, anoxygen atom (═O), —COOR″, —OC(═O)R″, a cyano group, a nitro group,—NR″₂, —R⁹′-N(R¹⁰′)—C(═O)—O—R⁵′, and a nitrogen-containing heterocyclicgroup.

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

The alkoxy group for the substituent is preferably an alkoxy group of 1to 6 carbon atoms. The alkoxy group is preferably a linear or branchedgroup. Specific examples include groups in which an oxygen atom (—O—) isbonded to any of the alkyl groups described above as the substituent.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

As examples of the halogenated alkyl group for the substituent, groupsin which part or all of the hydrogen atoms of the aforementioned alkylgroups for the substituent have been substituted with the aforementionedhalogen atoms can be given. As the halogenated alkyl group, afluorinated alkyl group is preferable, and a perfluoroalkyl group isparticularly desirable.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

In the —COOR″ group, the —OC(═O)R″ group and the —NR″₂ group, R″represents a hydrogen atom or a linear, branched or cyclic alkyl groupof 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The two R″ groups within the —NR″₂ group may be the same or differentfrom each other.

In formula —R⁹′-N(R¹⁰′)—C(═O)—O—R⁵′, R⁹′ represents a divalenthydrocarbon group which may contain a hetero atom, R¹⁰′ represents ahydrogen atom or a monovalent hydrocarbon group which may contain ahetero atom, and R⁵′ represents a monovalent organic group which has analiphatic ring or an aromatic ring.

Examples of the hydrocarbon group for R⁹′ include groups in which onehydrogen atom has been removed from the hydrocarbon group for R¹ in theaforementioned formula (C1).

As examples of R¹⁰′ and R⁵′, the same groups as those described abovefor R² and R³ in formula (C1) can be given, respectively.

In formula —R⁹′—N(R¹⁰′)—C(═O)—O—R⁵′, R¹⁰′ may be bonded to R⁹′ to form aring.

With respect to R¹ and R² in formula (C1), when R¹ has—R⁹′-N(R¹⁰′)—C(═O)—O—R⁵′ as a substituent, R¹⁰′ may be bonded to R² informula (C1) to form a ring.

With respect to R¹ and R² in formula (C1), when R¹ has—R⁹′—N(R¹⁰′)—C(═O)—O—R⁵′ as a substituent, the compound represented byformula (C1) is preferably a compound represented by the followinggeneral formula: R⁵′—O—C(═O)—N(R¹⁰′)—R⁴—N(R²)—C(═O)—O—R³ [in theformula, R², R³, R¹⁰′ and R⁵′ are the same as defined above; and R⁴represents a divalent aliphatic hydrocarbon group].

Examples of the divalent aliphatic hydrocarbon group for R⁴ includegroups in which one hydrogen atom has been removed from the aliphatichydrocarbon groups for R¹ and R² described later.

The “nitrogen-containing heterocyclic group” as the aforementionedsubstituent is a group in which one or more hydrogen atoms have beenremoved from a nitrogen-containing heterocyclic compound containing anitrogen atom in the ring skeleton thereof. The nitrogen-containingheterocyclic compound may have a carbon atom or a hetero atom other thannitrogen (e.g., an oxygen atom, a sulfur atom or the like) within thering skeleton thereof.

The nitrogen-containing heterocyclic compound may be either aromatic oraliphatic. When the nitrogen-containing heterocyclic compound isaliphatic, it may be either saturated or unsaturated. Further, thenitrogen-containing heterocyclic compound may be either monocyclic orpolycyclic.

The nitrogen-containing heterocyclic compound preferably has 3 to 30carbon atoms, more preferably 5 to 30, and still more preferably 5 to20.

Specific examples of monocyclic nitrogen-containing heterocyclc compoundinclude pyrrole, pyridine, imidazole, pyrazole, 1,2,3-triazole,1,2,4-triazole, pyrimidine, pyrazine, 1,3,5-triazine, tetrazole,piperidine, piperazine, pyrrolidine and morpholine.

Specific examples of polycyclic nitrogen-containing heterocyclc compoundinclude quinoline, isoquinoline, indole, pyrrolo[2,3-b]pyridine,indazole, benzimidazole, benzotriazole, carbazole, acridine,1,5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene,hexamethylenetetramine and 1,4-diazabicyclo[2.2.2]octane.

The nitrogen-containing heterocyclic compound may have a substituent.Examples of the substituent include the same groups as those describedabove for the substituent group which substitutes a hydrogen atom bondedto the aromatic ring contained in the aforementioned aromatichydrocarbon group.

In formula (C1), the aliphatic hydrocarbon group for R¹ and R² refers toa hydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group for R¹ and R² may be either saturated(an alkyl group) or unsaturated. In general, the aliphatic hydrocarbongroup is preferably saturated. Further, the aliphatic hydrocarbon groupmay be linear, branched or cyclic, or a combination thereof. Examples ofthe combination include a group in which a cyclic aliphatic hydrocarbongroup is bonded to a terminal of a linear or branched aliphatichydrocarbon group, and a group in which a cyclic aliphatic hydrocarbongroup is interposed within a linear or branched aliphatic hydrocarbongroup.

The linear or branched alkyl group preferably has 1 to 20 carbon atoms,more preferably 1 to 15, and still more preferably 1 to 10.

Specific examples of linear alkyl groups include a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, an octyl group, a nonyl group, a decyl group, anundecyl group, a dodecyl group, a tridecyl group, an isotridecyl group,a tetradecyl group, a pentadecyl group, a hexadecyl group, anisohexadecyl group, a heptadecyl group, an octadecyl group, a nonadecylgroup, an icosyl group, a henicosyl group and a docosyl group.

Specific examples of branched alkyl groups include a 1-methylethyl group(an isopropyl group), a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a tert-butyl group, a1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group anda 4-methylpentyl group.

The cyclic alkyl group may be either a monocyclic group or a polycyclicgroup. The aliphatic cyclic group preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. As the aliphatic cyclicgroup, a group in which one hydrogen atom has been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane can be used. Specific examples of thegroup in which one hydrogen atom has been removed from a monocycloalkaneinclude a cyclopentyl group and a cyclohexyl group. Examples of thegroup in which one hydrogen atom has been removed from a polycycloalkaneinclude an adamantyl group, a norbornyl group, an isobornyl group, atricyclodecyl group and a tetracyclododecyl group.

The aliphatic hydrocarbon group may have a substituent. For example,part of the carbon atoms constituting the aliphatic hydrocarbon groupmay be replaced by a divalent linking group containing a hetero atom,and part or all of the hydrogen atoms constituting the aliphatichydrocarbon group may be substituted with a substituent.

With respect to the divalent linking group containing a hetero atom,examples of hetero atoms include the same hetero atoms as thosedescribed above which replaces part of the carbon atoms constituting thearomatic ring contained in the aforementioned aromatic hydrocarbongroup. Examples of the divalent linking group containing a hetero atominclude divalent non-hydrocarbon groups containing a hetero atom, suchas —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —S—,—S(═O)₂, —S(═O)₂—O—, —NH—, —NR⁰⁴—R⁰⁴ represents a substituent such as analkyl group or an acyl group), —NH—C(═O)— and ═N—. Further, acombination of any one of these “divalent non-hydrocarbon groupscontaining a hetero atom” with a divalent aliphatic hydrocarbon groupcan also be used. Examples of the divalent aliphatic hydrocarbon groupinclude groups in which one hydrogen atom has been removed from theaforementioned aliphatic hydrocarbon group, and a linear or branchedaliphatic hydrocarbon group is preferable.

As the substituent for the aliphatic hydrocarbon group in the latterexample, the same groups as those described above for the substituentgroup which substitutes a hydrogen atom bonded to the aromatic ringcontained in the aforementioned aromatic hydrocarbon group can bementioned.

In the aforementioned general formula (C1), R¹ and R² may be mutuallybonded to form a cyclic group with the adjacent nitrogen atom.

The cyclic group may be either an aromatic cyclic group or an aliphaticcyclic group. When the cyclic group is an aliphatic cyclic group, it maybe either saturated or unsaturated. In general, the aliphatic cyclicgroup is preferably saturated.

The cyclic group may have a nitrogen atom other than the nitrogen atombonded to R¹ and R² within the ring skeleton thereof. Further, thecyclic group may have a carbon atom or a hetero atom other than nitrogen(e.g., an oxygen atom, a sulfur atom or the like) within the ringskeleton thereof.

The cyclic group may be either a monocyclic group or a polycyclic group.

When the cyclic group is monocyclic, the number of atoms constitutingthe skeleton of the cyclic group is preferably from 4 to 7, and morepreferably 5 or 6. That is, the cyclic group is preferably a 4- to7-membered ring, and more preferably a 5- or 6-membered ring. Specificexamples of monocyclic groups include groups in which the hydrogen atomof —NH— has been removed from a heteromonocyclic group containing —NH—in the ring structure thereof, such as piperidine, pyrrolidine,morpholine, pyrrole, imidazole, pyrazole, 1,2,3-triazole,1,2,4-triazole, tetrazole or piperazine.

When the cyclic group is polycyclic, the cyclic group is preferablybicyclic, tricyclic or tetracyclic. Further, the number of atomsconstituting the skeleton of the cyclic group is preferably from 7 to12, and more preferably from 7 to 10. Specific examples of polycyclicnitrogen-containing heterocyclic groups include groups in which thehydrogen atom of —NH— has been removed from a heteropolycyclic groupcontaining —NH— in the ring structure thereof, such as indole,isoindole, carbazole, benzimidazole, indazole or benzotriazole.

The cyclic group may have a substituent. Examples of the substituentinclude the same groups as those described above for the substituentgroup which substitutes a hydrogen atom bonded to the aromatic ringcontained in the aforementioned aromatic hydrocarbon group.

As a cyclic group formed by R¹ and R² mutually bonded with the adjacentnitrogen atom, a group represented by general formula (II) shown belowis particularly desirable.

In the formula, R⁵ and R⁶ each independently represents a hydrogen atomor an alkyl group; R⁷ represents a linear alkylene group of 1 to 3carbon atoms which may have a carbon atom substituted with an oxygenatom or a nitrogen atom and may have a hydrogen atom substituted with asubstituent.

In formula (II), as the alkyl group for R⁵ and R⁶, the same alkyl groupsas those described above as the aliphatic hydrocarbon group for R¹ andR² can be mentioned, a linear or branched alkyl group is preferable, anda methyl group is particularly desirable.

Examples of the alkylene group for R⁷ which may have a carbon atomsubstituted with an oxygen atom or a nitrogen atom include —CH₂—,—CH₂—O—, —CH₂—NH—, —CH₂—CH₂—, —CH₂—O—CH₂—, —CH₂—NH—CH₂—, —CH₂—CH₂—CH₂—,—CH₂—CH₂—O—CH₂—, and —CH₂—CH₂—NH—CH₂—.

As the substituent which substitutes a hydrogen atom in the alkylenegroup, the same groups as those described above for the substituentgroup which substitutes a hydrogen atom bonded to the aromatic ringcontained in the aforementioned aromatic hydrocarbon group can bementioned. The hydrogen atom to be substituted with a substituent may bea hydrogen atom bonded to a carbon atom, or a hydrogen atom bonded to anitrogen atom.

In formula (C1), R³ represents a monovalent photoactive group.

The term “photoactive group” refers to a group which absorbs theexposure energy of the exposure conducted in step (2).

As the photoactive group, a ring-containing group is preferable, and maybe either a hydrocarbon ring or a hetero ring. Preferable examplesthereof include groups having a ring structure described above for R¹and R², and groups having an aromatic ring. Specific examples ofpreferable ring skeletons for the ring-containing group include benzene,biphenyl, indene, naphthalene, fluorene, anthracene, phenanthrene,xanthone, thioxanthone and anthraquinone.

Further, these ring skeletons may have a substituent. In terms ofefficiency in the generation of a base, as the substituent, a nitrogroup is particularly desirable.

As the component (C1), a compound represented by general formula (C1-11)or (C1-12) shown below is particularly desirable.

In the formulae, R^(4a) and R^(4b)) each independently represents a ringskeleton selected from benzene, biphenyl, indene, naphthalene, fluorene,anthracene, phenanthrene, xanthone, thioxanthone and anthraquinone whichmay have a substituent; R^(1a) and R^(2a) each independently representsan alkyl group of 1 to 15 carbon atoms or a cycloalkyl group; R^(11a)represents an alkyl group of 1 to 5 carbon atoms; m″ represents 0 or 1;n″ represents 0 to 3; and each p″ independently represents 0 to 3.

In formulae (C1-11) and (C1-12), in terms of efficiency in generation ofa base, it is preferable that R^(4a) and R^(4b)) has a nitro group as asubstituent, and it is particularly desirable that the ortho position issubstituted.

In terms of suppressing the diffusion length of the generated base, itis preferable that each of R^(1a) and R^(2a) is a cycloalkyl group of 5to 10 carbon atoms.

m″ is preferably 1. n″ is preferably 0 to 2. p″ is preferably 0 or 1.

Specific examples of the component (C1) are shown below.

Further, as a preferable example of the component (C), a compoundrepresented by general formula (C2) shown below (hereafter, referred toas “component (C2)”) can also be mentioned.

After absorbing the exposure energy by the exposure conducted in step(2), the component (C2) has the (—CH═CH—C(═O)—) portion isomerized to acis isomer, and is further cyclized by heating, thereby generating abase (NHR¹R²).

The component (C2) is preferable in that, not only a base can begenerated, but also the effect of rendering the resist compositionhardly soluble in an alkali developing solution in step (4) can beobtained.

In formula (C2), R¹ and R² are respectively the same as defined for R¹and R² in the aforementioned formula (C1); and R³′ represents anaromatic cyclic group having a hydroxy group on the ortho position.

In the aforementioned formula (C2), it is preferable that R¹ and R² aremutually bonded together with the adjacent nitrogen atom to form acyclic group represented by the aforementioned formula (II). Further, R¹and R² are preferably the same as defined for R^(1a) and R^(2a) in theaforementioned formula (C1-12).

As the aromatic cyclic group for R³′, the same groups having an aromaticring as those described above for R³ in the aforementioned formula (C1)can be mentioned. As the ring skeleton, benzene, biphenyl, indene,naphthalene, fluorene, anthracene and phenanthrene are preferable, and abenzene ring is more preferable.

The aromatic cyclic group for R³′ may have a substituent other than thehydroxy group on the ortho position. Examples of the substituent includea halogen atom, a hydroxy group, a mercapto group, a sulfide group, asilyl group, a silanol group, a nitro group, a nitroso group, a sulfinogroup, a sulfo group, a sulfonate group, a phosphino group, a phosphinylgroup, a phosphono group, a phosphonate group, an amino group, anammonio group, and a monovalent organic group such as an alkyl group.

Specific examples of the component (C2) are shown below.

Further, as a preferable example of the component (C), a compoundrepresented by general formula (C3) shown below (hereafter, referred toas “component (C3)”) can also be mentioned.

After absorbing the exposure energy by the exposure conducted in step(2), the component (C3) undergoes decarboxylation, and then reacts withwater to generate amine (base).

In the formula, R^(a) and R^(d) each independently represents a hydrogenatom or a hydrocarbon group of 1 to 30 carbon atoms which may have asubstituent (provided that, when both R^(a) and R^(d) represent ahydrocarbon group of 1 to 30 carbon atoms which may have a substituent,R^(a) and R^(d) are mutually bonded to form a ring); and R^(b)represents an aryl group which may have a substituent or an aliphaticcyclic group which may have a substituent.

In the aforementioned formula (C3), R^(a) represents a hydrogen atom ora hydrocarbon group of 1 to 30 carbon atoms which may have asubstituent.

The hydrocarbon group of 1 to 30 carbon atoms for R^(a) which may have asubstituent may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon group preferably has 5 to 30 carbonatoms, more preferably 5 to 20 carbon atoms, still more preferably 6 to15 carbon atoms, and most preferably 6 to 12 carbon atoms. Here, thenumber of carbon atoms within a substituent(s) is not included in thenumber of carbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 to 3, andmost preferably 1 or 2.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for theaforementioned aromatic hydrocarbon group include groups in which partor all of the hydrogen atoms within an alkyl group of 1 to 5 carbonatoms (e.g., a methyl group, an ethyl group, a propyl group, an n-butylgroup or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The aliphatic hydrocarbon group for R^(a) in the aforementioned formula(C3) may be either a saturated aliphatic hydrocarbon group, or anunsaturated aliphatic hydrocarbon group. Further, the aliphatichydrocarbon group may be linear, branched or cyclic.

In the aliphatic hydrocarbon group for R^(a) in the aforementionedformula (C3), part of the carbon atoms constituting the aliphatichydrocarbon group may be substituted with a substituent group containinga hetero atom, or part or all of the hydrogen atoms constituting thealiphatic hydrocarbon group may be substituted with a substituent groupcontaining a hetero atom.

As the “hetero atom” for R^(a) in the aforementioned formula (C3), thereis no particular limitation as long as it is an atom other than carbonand hydrogen. Examples of the halogen atom include a fluorine atom, achlorine atom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The cyclic aliphatic hydrocarbon group (aliphatic cyclic group) forR^(a) in the aforementioned formula (C3) is an aliphatic cyclic group of3 to 30 carbon atoms which may have a substituent.

In the aliphatic cyclic group for R^(a) in the aforementioned formula(C3), part of the carbon atoms constituting the aliphatic cyclic groupmay be substituted with a substituent group containing a hetero atom, orpart or all of the hydrogen atoms constituting the aliphatic cyclicgroup may be substituted with a substituent group containing a heteroatom.

As the “hetero atom” for R^(a) in the aforementioned formula (C3), thereis no particular limitation as long as it is an atom other than carbonand hydrogen, and examples thereof include a halogen atom, an oxygenatom, a sulfur atom and a nitrogen atom. Examples of the halogen atominclude a fluorine atom, a chlorine atom, an iodine atom and a bromineatom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. These substituents may becontained in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group has 3 to 30 carbon atoms,preferably 5 to 30, more preferably 5 to 20, still more preferably 6 to15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulae (L1) to (L6) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

In the formulae, the alkylene group for Q″ and R⁹⁴ to R⁹⁵ is preferablya linear or branched alkylene group, and has 1 to 5 carbon atoms,preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—, and —CH(CH₂CH₃)CH₂—;a trimethylene group (n-propylene group) [—CH₂CH₂CH₂—];alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; atetramethylene group [—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups suchas —CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group[—CH₂CH₂CH₂CH₂CH₂—].

In these aliphatic cyclic groups, part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

Examples of the alkoxy group and the halogen atom include the samegroups and atoms as those listed above for the substituent used forsubstituting part or all of the hydrogen atoms of the aliphatic cyclicgroup for R^(a).

As the aliphatic cyclic group for R^(a) which may have a substituent, analiphatic polycyclic group which may have a substituent is preferable.As the aliphatic polycyclic group, the aforementioned group in which oneor more hydrogen atoms have been removed from a polycycloalkane, andgroups represented by formulae (L2) to (L6), (S3) and (S4) arepreferable.

When R^(a) in the aforementioned formula (C3) represents a hydrocarbongroup of 1 to 30 carbon atoms which may have a substituent, R^(a) mayform a ring with the adjacent carbon atom. The formed ring may be eithermonocyclic or polycyclic. The number of carbon atoms (including thecarbon atom bonded thereto) is preferably 5 to 30, and more preferably 5to 20.

Specifically, among the cyclic aliphatic hydrocarbon groups (aliphaticcyclic groups) for R^(a) described above, aliphatic cyclic groups of 5to 30 carbon atoms can be given as examples (provided that the carbonatom bonded thereto is regarded as part of the ring).

It is preferable that R^(a) in the aforementioned formula (C3) is ahydrogen atom or a cyclic group which may have a substituent. The cyclicgroup may be either an aromatic hydrocarbon group which may have asubstituent, or an aliphatic cyclic group which may have a substituent.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulae (L2) to (L6), (S3) and (S4) are preferable.

As the aromatic hydrocarbon group which may have a substituent, anaphthyl group which may have a substituent, or a phenyl group which mayhave a substituent is preferable.

Examples of the aryl group for R^(b) in the aforementioned formula (C3)include the aromatic hydrocarbon groups described above for R^(a),excluding arylalkyl groups. As the aryl group for R^(b), a phenyl groupis more preferable.

The aliphatic cyclic group for R^(b) in the aforementioned formula (C3)is the same as defined for the aliphatic cyclic group for R^(a) in theaforementioned formula (C3). The aliphatic cyclic group for R^(b) ispreferably an aliphatic polycyclic group, more preferably a group inwhich one or more hydrogen atoms have been removed from apolycycloalkane, and most preferably a group in which one or morehydrogen atoms have been removed from adamantane.

As the substituent which the aromatic hydrocarbon group or the aliphaticcyclic group for R^(b) may have, the same substituents as thosedescribed above for R^(a) in the aforementioned formula (C3) can bementioned.

R^(d) in the aforementioned formula (C3) is the same as defined forR^(a) in the aforementioned formula (C3).

It is preferable that R^(d) in the aforementioned formula (C3) is acyclic group which may have a substituent.

The cyclic group may be either an aromatic hydrocarbon group which mayhave a substituent, or an aliphatic cyclic group which may have asubstituent, and an aromatic cyclic group which may have a substituentis preferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulae (L2) to (L6), (S3) and (S4) are preferable.

R^(d) in the aforementioned formula (C3) is more preferably a naphthylgroup which may have a substituent, or a phenyl group which may have asubstituent, and most preferably a phenyl group which may have asubstituent.

When both R^(a) and R^(d) in the aforementioned formula (C3) represent ahydrocarbon group of 1 to 30 carbon atoms which may have a substituent,R^(a) and R^(d) are mutually bonded to form a ring. The formed ring maybe either monocyclic or polycyclic. The number of carbon atoms(including the carbon atom bonded to R^(a) and R^(d) in theaforementioned formula (C3) is preferably 5 to 30, and more preferably 5to 20.

Specifically, among the cyclic aliphatic hydrocarbon groups (aliphaticcyclic groups) for R^(a) described above, aliphatic cyclic groups of 5to 30 carbon atoms can be given as examples, provided that the carbonatom bonded to R^(a) and R^(d) in the aforementioned formula (C3) isregarded as part of the ring.

Specific examples of the component (C3) are shown below.

Further, as a preferable example of the component (C), the followingacyloxyimino group-containing compounds (C4) can also be mentioned.

In the formulae, R¹¹, R¹², R⁴³ and R⁴⁴ each independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms; and n7 to n10each independently represents 0 to 3.

Furthermore, as the component (C), other than the above examples, any ofthe known photo-base generators used in conventional chemicallyamplified resist compositions can be used.

Examples of such photo-base generators include ion-type photo-basegenerators (anion-cation complexes); triphenylsulfonium compounds;triphenylmethanol; photoactive carbamates, such as benzylcarbamate andbenzoin carbamate; amides, such as o-carbamoylhydroxylamide,o-carbamoyloxime, aromatic sulfoneamide, alphalactum andN-(2-allylethynyl)amide; oximeesters; α-aminoacetophenone; cobaltcomplexes; and those exemplified in Japanese Unexamined PatentApplication, First Publication No. 2007-279493.

As the component (C), one type of organic compound may be used alone, ortwo or more types of organic compounds may be used in combination.

Among these, as the component (C), the component (C1) is preferable,more preferably at least one compound selected from a compoundrepresented by any one of general formulas (C1-11) and (C1-12). Thecompound represented by general formula (C1-12) is particularlydesirable.

In the resist composition, the amount of the component (C), relative to100 parts by weight of the component (A) is preferably from 0.05 to 50parts by weight, more preferably from 1 to 30 parts by weight, and stillmore preferably from 5 to 20 parts by weight, and most preferably from 2to 20 parts by weight.

When the amount of the component (C) is at least as large as the lowerlimit of the above-mentioned range, the film retentiveness of the resistfilm at exposed portions becomes excellent, and the resolution of theformed resist pattern is enhanced. On the other hand, when the amount ofthe component (C) is no more than the upper limit of the above-mentionedrange, the transparency of the resist film can be maintained.

Acid Supply Component; Component (Z)

In the step (1) of the method of forming a resist pattern according tothe present invention, the resist composition including an “acid supplycomponent” which supplies an acid which is provided to the resist filmis used.

In the present invention, the “acid supply component” includes acomponent that exhibits acidity by itself, that is, a component actingas a proton donor (hereafter, referred to as “acidic compound component”or “component (G)”); and a component which is decomposed by heat orlight to act as an acid (hereafter, referred to as “acid generatorcomponent” or “component (B)”).

Acidic Compound Component; Component (G)

In the present invention, as the component (G), an acid salt (hereafter,referred to as “component (G1)”) having an acid strength capable ofincreasing the solubility of the base component (A) in an alkalideveloping solution, or an acid (an acid not forming a salt, and an acidnot being ionic; hereafter, referred to as “component (G2)”) other thanthe acid salt can be used.

An acid “has an acid strength sufficient for increasing the solubilityof the base component (A) in an alkali developing solution” includesacid, for example, when a polymeric compound (A1) having a structuralunit (a1) is used, by conducting baking (PEB) in the aforementioned step(3), the acid is capable of causing cleavage of at least part of thebond within the structure of the acid decomposable group in thestructural unit (a1).

As another aspect of the component (G) according to the presentinvention, the component (G) includes a compound (G1C) (hereafter,referred to as “component (G1C)”) composed of a nitrogen-containingcation having a pKa value of 7 or less and a counteranion.

[Component (G1)]

Examples of the component (G1) include an ionic compound (salt compound)composed of a nitrogen-containing cation and a counteranion. Even ifforming a salt, the component (G1) exhibits acidity by itself, and actsas a proton donor.

Hereafter, each of the cation moiety and the anion moiety in thecomponent (G1) will be described.

(Cation Moiety of Component (G1))

The structure of the cation moiety in the component (G1) is notparticularly limited as long as it contains a nitrogen atom. As specificexamples of the cation moiety in the component (G1), a cationrepresented by general formula (G1c-1) shown below is particularly used.

In the formula, R^(101d), R^(101e), R^(101f) and R^(101g) eachindependently represents a hydrogen atom, a linear, branched or cyclicalkyl group, an alkenyl group, an oxoalkyl group or an oxoalkenyl groupof 1 to 12 carbon atoms, an aryl group or an arylalkyl group of 6 to 20carbon atoms, an aralkyl group of 7 to 12 carbon atoms or anaryloxoalkyl group, and part or all of the hydrogen atoms of thesegroups may be substituted with a halogen atom, an alkoxy group or asulfur atom. R^(101d) and R^(101e), or R^(101d), R^(101e) and R^(101f)may be mutually bonded with the nitrogen atom to form a ring, providedthat, when a ring is formed, each of R^(101d) and R^(101e), or each ofR^(101d), R^(101e) and R^(101f) independently represents an alkylenegroup of 3 to 10 carbon atoms, or forms a heteroaromatic ring containingthe nitrogen atom in the ring thereof.

In formula (G1c-1), R^(101d), R^(101e), R^(101f) and R^(101g)independently represents a hydrogen atom, a linear, branched or cyclicalkyl group, an alkenyl group, an oxoalkyl group or an oxoalkenyl groupof 1 to 12 carbon atoms, an aryl group or an arylalkyl group of 6 to 20carbon atoms, an aralkyl group of 7 to 12 carbon atoms or anaryloxoalkyl group.

The alkyl group for R^(101d) to R^(101g) includes the same alkyl groupsas those described for the aforementioned R¹ and R², although the alkylgroup for R^(101d) to R^(101g) preferably has 1 to 10 carbon atoms, anda methyl group, an ethyl group, a propyl group or a butyl group isparticularly desirable.

The alkenyl group for R^(101d) to R^(101g) preferably has 2 to 10 carbonatoms, more preferably 2 to 5, and still more preferably 2 to 4.Specific examples thereof include a vinyl group, a propenyl group (anallyl group), a butynyl group, a 1-methylpropenyl group and a2-methylpropenyl group.

The oxoalkyl group for R^(101d) to R^(101g) preferably has 2 to 10carbon atoms, and examples thereof include a 2-oxoethyl group, a2-oxopropyl group, a 2-oxocyclopentyl group and a 2-oxocyclohexyl group.

Examples of the oxoalkenyl group for R^(101d) to R^(101g) include anoxo-4-cyclohexenyl group and a 2-oxo-4-propenyl group.

As examples of the aryl group for R^(101d) to R^(101g), the same arylgroups as those described above in the aromatic hydrocarbon groups forR¹ and R² can be mentioned, and a phenyl group or a naphthyl group ispreferable. Examples of the arylalkyl group include aryl groups in whichone or more hydrogen atoms have been substituted with an alkyl group(preferably an alkyl group of 1 to 5 carbon atoms).

Examples of the aralkyl group and aryloxoalkyl group for R^(101d) toR^(101g) include a benzyl group, a phenylethyl group, a phenethyl group,a 2-phenyl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl group and a2-(2-naphthyl)-2-oxoethyl group.

The hydrogen atoms within the alkyl group, the alkenyl group, theoxoalkyl group, the oxoalkenyl group, the aryl group, the arylalkylgroup, the aralkyl group and the aryloxoalkyl group for R^(101d) toR^(101g) may or may not be substituted with a halogen atom such as afluorine atom, an alkoxy group or a sulfur atom.

When R^(101d) to R^(101g) are constituted of only a combination of alkylgroups and hydrogen atoms, in terms of storage stability and lithographyproperties, it is preferable that part of the hydrogen atoms of thealkyl group is substituted with a halogen atom such as a fluorine atom,an alkoxy group or a sulfur atom.

Further, R^(101d) and R^(101e), or R^(101d), R^(101e) and R^(101f) maybe mutually bonded to form a ring with the nitrogen atom. Examples ofthe formed ring include a piperidine ring, a hexamethylene imine ring,an azole ring, a pyridine ring, a pyrimidine ring, an azepine ring, apyrazine ring, a quinoline ring and a benzoquinoline ring.

Further, the ring may contain an oxygen atom in the ring skeletonthereof, and specific examples of preferable rings which contain anoxygen atom include an oxazole ring and an isooxazole ring.

Among these examples, as the cation moiety represented by theaforementioned formula (G1c-1), a nitrogen-containing cation having apKa of 7 or less is preferable.

In the present invention, pKa refers to an acid dissociation constantwhich is generally used as a parameter which shows the acid strength ofan objective substance. The pKa value of the cation of the component(G1) can be determined by a conventional method. Alternatively, the pKavalue can be estimated by calculation using a conventional software suchas “ACD/Labs” (trade name; manufactured by Advanced ChemistryDevelopment, Inc.).

The pKa of the component (G1) is preferably 7 or less, and the component(G1) can be appropriately selected depending on the type and pKa of thecounteranion, so that is becomes a weak base relative to thecounteranion. Specifically, the pKa of the component (G1) is preferablyfrom −2 to 7, more preferably from −1 to 6.5, and still more preferably0 to 6. When the pKa is no more than the upper limit of theabove-mentioned range, the basicity of the cation can be renderedsatisfactorily weak, and the component (G1) itself becomes an acidiccompound. Further, when the pKa is at least as large as the lower limitof the above-mentioned range, a salt can be more reliably formed withthe counteranion, and it becomes possible to appropriately control theacidity of the component (G1), thereby preventing deterioration of thestorage stability caused by the component (G1) being excessively acidic.

As a cation which satisfies the above pKa, a cation represented by anyone of the following general formulae (G1c-11) to (G1c-13) isparticularly desirable.

In the formulae, Rf^(g1) represents a fluorinated alkyl group of 1 to 12carbon atoms; Rn^(g1) and Rn^(g2) each independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms, provided thatRn^(g1) and R^(g2) may be mutually bonded to form a ring; Q^(a) to Q^(c)each independently represents a carbon atom or a nitrogen atom; Rn^(g3)represents a hydrogen atom or a methyl group; Rn^(g4) and Rn^(g5) eachindependently represents an alkyl group of 1 to 5 carbon atoms or anaromatic hydrocarbon group; R^(g1) and R^(g2) each independentlyrepresents a hydrocarbon group; and n15 and n16 each independentlyrepresents an integer of 0 to 4, provided that, when n15 and n16 is 2 ormore, the plurality of R^(g1) and R^(g2) which substitute the hydrogenatoms of the adjacent carbon atom may be bonded to form a ring.

In formula (G1c-11), Rf^(g1) represents a fluorinated alkyl group of 1to 12 carbon atoms, and is preferably a fluorinated alkyl group of 1 to5 carbon atoms in which 50% or more of the hydrogen atoms of the alkylgroup have been fluorinated.

In formula (G1c-11), each of Rn^(g1) and Rn^(g2) independentlyrepresents a hydrogen atom or an alkyl group of 1 to 5 carbon atoms. Asthe alkyl group, the same alkyl groups of 1 to 5 carbon atoms as thosedescribed above in formula (G1c-1) can be mentioned. In addition, whenboth of Rn^(g1) and Rn^(g2) represent alkyl groups, alkyl groups forRn^(g1) and Rn^(g2) may be mutually bonded to form a ring together withNH⁺ in the formula.

In formula (G1c-13), Rn^(g4) and Rn^(g5) each independently representsan alkyl group of 1 to 5 carbon atoms or an aromatic hydrocarbon group,and is the same as defined for the alkyl group of 1 to 5 carbon atomsand aryl groups as those described above in the explanation of R^(101d),R^(101e), R^(101f) and d R^(101g) in formula (G1c-1).

In formulae (G1c-12) and (G1c-13), n15 and n16 each independentlyrepresents an integer of 0 to 4, preferably an integer of 0 to 2, andmore preferably 0.

In formulae (G1c-12) and (G1c-13), R^(g1) and R^(g2) each independentlyrepresents a hydrocarbon group, and is preferably an alkyl group oralkenyl group of 1 to 12 carbon atoms. The alkyl group and the alkenylgroup are the same as defined for those described in the explanation offormula (G1c-1).

When n15 and n16 are 2 or more, the plurality of R^(g1) and R^(g2) maybe the same or different from each other. Further, when n15 and n16 is 2or more, the plurality of R^(g1) and R^(g2) which substitute thehydrogen atoms of the adjacent carbon atom may be bonded to form a ring.Examples of the formed ring include a benzene ring and a naphthalenering. That is, the compound represented by formula (G1c-12) or (G1c-13)may be a condensed ring compound formed by condensation of 2 or morerings.

Specific examples of compounds represented by any one of theaforementioned formulae (G1c-11) to (G1c-13) are shown below.

(Anion Moiety of Component (G1))

The anion moiety of the component (G1) is not particularly limited, andany of those generally used the anion moiety of a salt used in a resistcomposition may be appropriately selected for use.

Among these, as the anion moiety of the component (G1), those whichforms a salt with the aforementioned cation moiety for the component(G1) to form a component (G1) that is capable of increasing thesolubility of the component (A) in an alkali developing solution ispreferable.

The component (G1) “capable of increasing the solubility of thecomponent (A) in an alkali developing solution” refers to a component(G1), for example, when a component (A1) having a structural unit (a1)is used, by conducting baking in the aforementioned step (3), thecomponent (G1) is capable of causing cleavage of at least part of thebond within the structure of the acid decomposable group in thestructural unit (a1).

That is, the anion moiety of the component (G1) preferably has a strongacidity. Specifically, the pKa of the anion moiety is more preferably 0or less, still more preferably −15 to −1, and most preferably −13 to −3.When the pKa of the anion moiety is no more than 0, the acidity of theanion can be rendered satisfactorily strong relative to a cation havinga pKa of 7 or less, and the component (G1) itself becomes an acidiccompound. On the other hand, when the pKa of the anion moiety is −15 ormore, deterioration of the storage stability caused by the component(G1) being excessively acidic can be prevented.

As the anion moiety of the component (G1), an anion moiety having atleast one anion group selected from a sulfonate anion, a carboxylateanion, a sulfonylimide anion, a bis(alkylsulfonyl)imide anion and atris(alkylsulfonyl)methide anion is preferable.

Specific examples include anions represented by general formula: “R⁴¹SO₃⁻ (R⁴″ represents a linear, branched or cyclic alkyl group which mayhave a substituent, a halogenated alkyl group, an aryl group or analkenyl group)”.

In the aforementioned general formula “R⁴″SO₃ ⁻”, R⁴″ represents alinear, branched or cyclic alkyl group which may have a substituent, ahalogenated alkyl group, an aryl group or an alkenyl group.

The linear or branched alkyl group for the aforementioned R⁴″ preferablyhas 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1to 4.

The cyclic alkyl group for the aforementioned R⁴″ preferably has 4 to 15carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably6 to 10 carbon atoms.

When R⁴″ represents an alkyl group, examples of “R⁴″SO₃ ⁻” includealkylsulfonates, such as methanesulfonate, n-propanesulfonate,n-butanesulfonate, n-octanesulfonate, 1-adamantanesulfonate,2-norbornanesulfonate and d-camphor-10-sulfonate.

The halogenated alkyl group for the aforementioned R⁴″ is an alkyl groupin which part or all of the hydrogen atoms thereof have been substitutedwith a halogen atom. The alkyl group preferably has 1 to 5 carbon atoms,and is preferably a linear or branched alkyl group, and more preferablya methyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, a tert-butyl group, a tert-pentyl group or an isopentylgroup. Examples of the halogen atom which substitutes the hydrogen atomsinclude a fluorine atom, a chlorine atom, an iodine atom and a bromineatom.

In the halogenated alkyl group, it is preferable that 50 to 100% of allhydrogen atoms within the alkyl group (prior to halogenation) have beensubstituted with a halogen atom, and it is preferable that all hydrogenatoms have been substituted with a halogen atom.

As the halogenated alkyl group, a fluorinated alkyl group is preferable.The fluorinated alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.

Further, the fluorination ratio of the fluorinated alkyl group ispreferably from 10 to 100%, more preferably from 50 to 100%, and it ismost preferable that all hydrogen atoms are substituted with fluorineatoms because the acid strength increases.

Specific examples of such fluorinated alkyl groups include atrifluoromethyl group, a heptafluoro-n-propyl group and anonafluoro-n-butyl group.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, and a group represented by the formula X³-Q′- (in theformula, Q′ represents a divalent linking group containing an oxygenatom; and X³ represents a hydrocarbon group of 3 to 30 carbon atomswhich may have a substituent).

Examples of halogen atoms and alkyl groups include the same halogenatoms and alkyl groups as those described above with respect to thehalogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

In the group represented by formula X³-Q′-, Q′ represents a divalentlinking group containing an oxygen atom.

Q′ may contain an atom other than an oxygen atom. Examples of atomsother than oxygen include a carbon atom, a hydrogen atom, a sulfur atomand a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl bond (—C(═O)—) and a carbonate bond(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.Furthermore, the combinations may have a sulfonyl group (—SO₂—) bondedthereto.

Specific examples of such combinations include —R⁹¹—O—, —R⁹²—O—C(═O)—,—C(═O)—O—R⁹³—O—C(═O)—, —SO₂—O—R⁹⁴—O—C(═O)—, and —R⁹⁵—SO₂—O—R⁹⁴—O—C(═O)—(in the formula, R⁹¹ to R⁹⁵ independently represents an alkylene group).

The alkylene group for R⁹¹ to R⁹⁵ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; a trimethylene group(n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as—CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group[—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

As Q′, a divalent linking group containing an ester bond or an etherbond is preferable, and —R⁹¹—O—, —R⁹²—O—C(═O)— or —C(═O)—O—R⁹³—O—C(═O)—is more preferable.

In the group represented by the formula X³-Q′-, as the hydrocarbon groupfor X³, the same hydrocarbon groups of 1 to 30 carbon atoms as thosedescribed for R^(a) in the aforementioned formula (C3).

Among these, as X³, a linear alkyl group which may have a substituent,or a cyclic group which may have a substituent is preferable. The cyclicgroup may be either an aromatic hydrocarbon group which may have asubstituent, or an aliphatic cyclic group which may have a substituent,and an aliphatic cyclic group which may have a substituent ispreferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, or any oneof groups represented by the aforementioned formulae (L2) to (L6), (S3)and (S4) are preferable.

Among these examples, as the aforementioned R⁴″, a halogenated alkylgroup or a group having X³-Q′-as a substituent is preferable.

When the R⁴″ group has X³-Q′-as a substituent, as R⁴″, a grouprepresented by the formula: X³-Q′-Y³— (in the formula, Q′ and X³ are thesame as defined above, and Y³ represents an alkylene group of 1 to 4carbon atoms which may have a substituent or a fluorinated alkylenegroup of 1 to 4 carbon atoms which may have a substituent is preferable.

In the group represented by the formula X³-Q′-Y³—, as the alkylene groupfor Y³, the same alkylene group as those described above for Q′ in whichthe number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group, the aforementioned alkylene group inwhich part or all of the hydrogen atoms has been substituted withfluorine atoms can be used.

Specific examples of Y³ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

Y³ is preferably a fluorinated alkylene group, and most preferably afluorinated alkylene group in which the carbon atom bonded to theadjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

Specific examples of groups represented by formula R⁴″SO₃ ⁻ in which R⁴″represents X³-Q′-Y³— include anions represented by the followingformulae (b1) to (b9).

In the formulae, q1 and q2 each independently represents an integer of 1to 5; q3 represents an integer of 1 to 12; t3 represents an integer of 1to 3; r1 and r2 each independently represents an integer of 0 to 3; grepresents an integer of 1 to 20; R⁷ represents a substituent; n1 to n6each independently represents 0 or 1; v0 to v6 each independentlyrepresents an integer of 0 to 3; w1 to w6 each independently representsan integer of 0 to 3; and Q″ is the same as defined above.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor R^(a) in the aforementioned formula (C3) may have as a substituentcan be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w6, then the two or more of the R⁷ groups may be the sameor different from each other.

Further, as preferable examples of the anion moiety of the component(G1), an anion represented by general formula (G1a-3) shown below and ananion moiety represented by general formula (G1a-4) shown below can alsobe mentioned.

In the formulae, X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; and each of Y″ and Z″ independently represents an alkyl group of 1to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom.

In formula (G1a-3), X″ represents a linear or branched alkylene group inwhich at least one hydrogen atom has been substituted with a fluorineatom, and the alkylene group preferably has 2 to 6 carbon atoms, morepreferably 3 to 5 carbon atoms, and most preferably 3 carbon atoms.

In formula (G1a-4), each of Y″ and Z″ independently represents a linearor branched alkyl group in which at least one hydrogen atom has beensubstituted with a fluorine atom, and the alkyl group preferably has 1to 10 carbon atoms, more preferably 1 to 7 carbon atoms, and mostpreferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved.

The amount of fluorine atoms within the alkylene group or alkyl group,i.e., fluorination ratio, is preferably from 70 to 100%, more preferablyfrom 90 to 100%, and it is particularly desirable that the alkylenegroup or alkyl group be a perfluoroalkylene or perfluoroalkyl group inwhich all hydrogen atoms are substituted with fluorine atoms.

As the anion moiety of the component (G1), an anion represented by theaforementioned formula “R⁴″SO₃ ⁻” (in particular, any one of anionsrepresented by the aforementioned formulae (b1) to (b9) which is a groupin which R⁴″ is “X³-Q′-Y³—”) or an anion represented by theaforementioned formula (G1a-3) is most preferable.

As the component (G1), one type of compound may be used alone, or two ormore types of compounds may be used in combination.

In the resist composition, the amount of the component (G1) within thecomponent (G) is preferably 40% by weight or more, still more preferably70% by weight or more, and may be even 100% by weight. When the amountof the component (G1) is at least as large as the lower limit of theabove-mentioned range, the storage stability and the lithographyproperties become excellent.

Further, in the case where the component (G) includes the component(G1), the amount of the component (G1) within the resist composition,relative to 100 parts by weight of the component (A) is preferably from0.5 to 30 parts by weight, more preferably from 1 to 20 parts by weight,and still more preferably from 2 to 15 parts by weight. When the amountof the component (G1) is within the above-mentioned range, thelithography properties become excellent.

[Component (G1C)]

In the present invention, the component (G1C) is an ionic compound (saltcompound) composed of a nitrogen-containing cation having a pKa value of7 or less and a counteranion. The component (G1C) contains the cationhaving a pKa value of 7 or less which has a relatively low pKa value,that is, a cation having low basicity. Therefore, even if forming asalt, the component (G1C) exhibits acidity by itself, and acts as aproton donor.

Hereafter, each of the cation moiety and the anion moiety in thecomponent (G1C) will be described.

(Cation Moiety of Component (G1C))

The cation moiety in the component (G1C) is composed of anitrogen-containing cation having a pKa value of 7 or less. In thepresent invention, pKa is the above-described acid dissociationconstant.

The pKa of the component (G1C) according to the present invention is notparticularly limited as long as it is 7 or less, and the component (G1C)can be appropriately selected depending on the type and pKa of thecounteranion, so that is becomes a weak base relative to thecounteranion, although the pKa of the cation of the component (G1C) ispreferably from −2 to 7.0, more preferably from −1 to 6.5, and stillmore preferably 0 to 6.0.

The structure of the cation moiety in the component (G1C) is notparticularly limited as long as it satisfies the above-mentioned pKavalue and contains a nitrogen atom. Examples thereof include the cationrepresented by following general formula (G1c-1C).

In the formula, R^(101d)′, R^(101e)′, R^(101f)′ and R^(101g)′ eachindependently represents a hydrogen atom, a linear, branched or cyclicalkyl group, an alkenyl group, an oxoalkyl group or an oxoalkenyl groupof 1 to 12 carbon atoms, an aryl group of 6 to 20 carbon atoms, anaralkyl group of 7 to 12 carbon atoms or an aryloxoalkyl group, and partor all of the hydrogen atoms of these groups may be substituted with afluorine atom or an alkoxy group. R^(101d)′ and R^(101e)′, or R^(101d)′,R^(101e)′ and R^(101f)′ may be mutually bonded with the nitrogen atom toform a ring, provided that, when a ring is formed, each of R^(101d)′ andR^(101e)′, or each of R^(101d)′, R^(101e)′ and R^(101f)′ independentlyrepresents an alkylene group of 3 to 10 carbon atoms, or forms aheteroaromatic ring containing the nitrogen atom in the ring thereof.When R^(101d)′, R^(101e)′, R^(101f)′ and R^(101g)′ are composed of onlyan alkyl group and/or a hydrogen atom, at least one atom of the hydrogenatoms and the carbon atoms is substituted with a halogen atom such as afluorine atom, an alkoxy group or a sulfur atom.

In formula (G1c-1C), R^(101d)′, R^(101e)′, R^(101f)′ and R^(101g)′independently represents a hydrogen atom, a linear, branched or cyclicalkyl group, an alkenyl group, an oxoalkyl group or an oxoalkenyl groupof 1 to 12 carbon atoms, an aryl group or an arylalkyl group of 6 to 20carbon atoms, an aralkyl group of 7 to 12 carbon atoms or anaryloxoalkyl group.

The alkyl group for R^(101d)′ to R^(101g)′ includes the same alkylgroups as those described for the aforementioned R¹ and R², although thealkyl group for R^(101d) to R^(101g) preferably has 1 to 10 carbonatoms, and a methyl group, an ethyl group, a propyl group or a butylgroup is particularly desirable.

The alkenyl group for R^(101d)′ to R^(101g)′ preferably has 2 to 10carbon atoms, more preferably 2 to 5, and still more preferably 2 to 4.Specific examples thereof include a vinyl group, a propenyl group (anallyl group), a butynyl group, a 1-methylpropenyl group and a2-methylpropenyl group.

The oxoalkyl group for R^(101d)′ to R^(101g)′ preferably has 2 to 10carbon atoms, and examples thereof include a 2-oxoethyl group, a2-oxopropyl group, a 2-oxocyclopentyl group and a 2-oxocyclohexyl group.

Examples of the oxoalkenyl group for R^(101d)′, to R^(101g)′ include anoxo-4-cyclohexenyl group and a 2-oxo-4-propenyl group.

As examples of the aryl group for R^(101d)′ to R^(101g)′, the same arylgroups as those described above in the aromatic hydrocarbon groups forR¹ and R² can be mentioned, and a phenyl group or a naphthyl group ispreferable.

Examples of the aralkyl group and aryloxoalkyl group for R^(101d)′ toR^(101g)′ include a benzyl group, a phenylethyl group, a phenethylgroup; a 2-phenyl-2-oxoethyl group, a 2-(1-naphthyl)-2-oxoethyl groupand a 2-(2-naphthyl)-2-oxoethyl group.

When R^(101d)′ to R^(101g)′ are composed of only an alkyl group and/or ahydrogen atom, at least one atom of the hydrogen atoms and the carbonatoms is substituted with a halogen atom such as a fluorine atom, analkoxy group or a sulfur atom. It is preferable that a hydrogen atom inthe alkyl group is substituted with a fluorine atom.

Further, R^(101d)′ and R^(101e)′, or R^(101d)′ R^(101e)′ and R^(101f)′may be mutually bonded to form a ring with the nitrogen atom. Examplesof the formed ring include a pyrrolidine ring, a piperidine ring, ahexamethylene imine ring, an azole ring, a pyridine ring, a pyrimidinering, an azepine ring, a pyrazine ring, a quinoline ring and abenzoquinoline ring.

Further, the ring may contain an oxygen atom in the ring skeletonthereof, and examples of preferable rings which contain an oxygen atominclude an oxazole ring and an isooxazole ring.

In particular, the cation moiety represented by the formula (G1c-1C) ispreferably cation moieties represented by the above-described generalformulae (G1c-11) to (G1c-13).

(Anion Moiety of Component (G1C))

As examples of the anion moiety of the component (G1C), the same asthose described for the anion moiety of the aforementioned component(G1) can be given.

As the component (G1C), one type of compound may be used alone, or twoor more types of compounds may be used in combination.

Further, in the resist composition of the present invention, the amountof the component (G1C) within the component (G) is preferably 40% byweight or more, still more preferably 70% by weight or more, and may beeven 100% by weight. When the amount of the component (G1C) is at leastas large as the lower limit of the above-mentioned range, the storagestability and the lithography properties become excellent.

Furthermore, in the resist composition, the amount of the component(G1C), relative to 100 parts by weight of the component (A) ispreferably from 0.5 to 30 parts by weight, more preferably from 1 to 20parts by weight, and still more preferably from 2 to 15 parts by weight.When the amount of the component (G1C) is within the above-mentionedrange, the storage stability and the lithography properties becomeexcellent.

In addition of the aforementioned component (G1C), the resistcomposition of the present invention may also include an acidic compoundcomponent (G2) other than the component (G1C) as the component (G), aslong as the effects of the present invention are not impaired.

[Component (G2)]

The component (G2) does not fall under the definition of the component(G1) and the component (G1C), and exhibits acidity by itself, and actsas a proton donor. As the component (G2), a non-ionic acid which doesnot form a salt can be mentioned.

The component (G2) is not particularly limited, as long as it has anacid strength capable of increasing the solubility of the base component(A) in the alkali developing solution. In terms of the reactivity withthe acid dissociable group of the base component and ease in increasingthe solubility of the resist film in an alkali developing solution, thecomponent (G2) preferably has a strong acidity. Specifically, the pKa ofthe component (G2) is more preferably 0 or less, still more preferably−15 to −1, and most preferably −13 to −3. When the pKa of the component(G2) is no more than 0, the component (G2) can satisfactorily have astrong acidity in increasing the solubility of the component (A) in analkali developing solution. On the other hand, when the pKa of thecomponent (G2) is −15 or more, deterioration of the storage stabilitycaused by the component (G2) being excessively acidic can be prevented.

As the component (G2), a carboxylic acid, an imine acid or a sulfonicacid compound is preferable, and more preferably at least one acidselected from a sulfonylimide, a bis(alkylsulfonyl)imide, atris(alkylsulfonyl)methide and a compound having a fluorine atom withinthese compounds. Among these acids, the compound having a fluorine atomwithin these compounds as a substituent is particularly desirable.

In particular, a compound represented by any one of general formulae(G2-1) to (G2-3) shown below (preferably a compound represented bygeneral formula (G2-2)), a compound in which an anion represented by anyone of general formulae (b1) to (b9) described above has “—SO₃ ⁻”replaced by “—SO₃H”, a compound in which an anion represented by generalformula (G1a-3) or (G1a-4) described above has “N⁻” replaced by “NH”,and camphorsulfonic acid are preferable. Other examples include acidcomponents such as a fluorinated alkyl group-containing carboxylic acid,a higher fatty acid, a higher alkylsulfonic acid, and a higheralkylarylsulfonic acid.

In formula (G2-1), w′ represents an integer of 1 to 5. In formula(G2-2), R^(f) represents a hydrogen atom or an alkyl group (providedthat part or all of the hydrogen atoms within the alkyl group may besubstituted with a fluorine atom, a hydroxy group, an alkoxy group, acarboxy group or an amino group); and y′ represents 2 or 3. In formula(G2-3), R^(f) is the same as defined above; and z′ represents 2 or 3.

Examples of compounds represented by the aforementioned formula (G2-1)include (C₄F₉SO₂)₂NH and (C₃F₇SO₂)₂NH.

In the aforementioned formula (G2-2), the alkyl group for R^(f)preferably has 1 or 2 carbon atoms, and more preferably 1.

Examples of the alkoxy group which may substitute the hydrogen atom(s)within the alkyl group include a methoxy group and an ethoxy group.

An example of a compound represented by the aforementioned formula(G2-2) includes a compound represented by a chemical formula (G2-21)shown below.

In the aforementioned formula (G2-3), R^(f) is the same as defined forR^(f) in formula (G2-2).

An example of a compound represented by the aforementioned formula(G2-3) includes a compound represented by a chemical formula (G2-31)shown below.

As the fluorinated alkyl group-containing carboxylic group, for example,C₁₀F₂₁COOH can be mentioned.

Examples of the higher fatty acid include higher fatty acids having analkyl group of 8 to 20 carbon atoms, and specific examples thereofinclude dodecanoic acid, tetradecanoic acid, and stearic acid.

The alkyl group of 8 to 20 carbon atoms may be either linear orbranched. Further, the alkyl group of 8 to 20 carbon atoms may have aphenylene group, an oxygen atom or the like interposed within the chainthereof. Furthermore, the alkyl group of 8 to 20 carbon atoms may havepart of the hydrogen atoms substituted with a hydroxy group or a carboxygroup.

Examples of the higher alkylsulfonic acid include sulfonic acids havingan alkyl group preferably with an average of 9 to 21 carbon atoms, morepreferably 12 to 18 carbon atoms, and specific examples thereof includedecanesulfonic acid, dodecanesulfonic acid, tetradecanesulfonic acid,tetradecanesulfonic acid, pentadecanesulfonic acid andoctadecanesulfonic acid.

Examples of the higher alkylarylsulfonic acid includealkylbenzenesulfonic acids and alkylnaphthalenesulfonic acids having analkyl group preferably with an average of 6 to 18 carbon atoms, morepreferably 9 to 15 carbon atoms, and specific examples thereof includedodecylbenzenesulfonic acid and decylnaphthalenesulfonic acid.

Examples of the acid components include alkyldiphenyletherdisulfonicacids preferably with an average of 6 to 18 carbon atoms, morepreferably 9 to 15, and preferable examples thereof includedodecyldiphenyletherdisulfonic acid.

Examples of the component (G2) other than those described above includeorganic carboxylic acid, a phosphorus oxo acid or derivative thereof.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonate esters suchas dimethyl phosphonate, di-n-butyl phosphonate, phenyl phosphonate,diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinate esters andphenylphosphinic acid.

When the component (G) includes the component (G2), as the component(G2), one type may be used, or two or more types may be used incombination. Among these, as the component (G2), one or more compoundsselected from the group consisting of a sulfonylimide, abis(alkylsulfonyl)imide, a tris(alkylsulfonyl)methide, an alkylsulfonicacid and a compound having a fluorine atom within these compounds arepreferably used, and one or more compounds having a fluorine atom withinthese compounds are particularly preferably used.

In the present invention, when the component (G) includes the component(G2), the pKa value of the component (G2) is preferably equal to or morethan that of the anion moiety of the component (G1C). That is, the pKavalue of the component (G2) is more preferably 0 or less, still morepreferably −15 to −1, and most preferably −13 to −3.

When the pKa value of the component (G2) is greater than or equal tothat of the anion moiety of the component (G1C) (i.e., when the anionmoiety of the component (G1C) has most strong acidity), cations of thecomponent (G1C) and the component (G2) can be prevented from beingexchanged.

When the component (G) includes the component (G2), the amount of thecomponent (G2) within the component (G) is preferably 50% by weight orless, more preferably 20% by weight or less.

In addition, when the resist composition includes the component (G2),the amount of the component (G2) in the resist composition, relative to100 parts by weight of the component (A) is preferably from 0.5 to 25parts by weight, more preferably from 1 to 20 parts by weight, stillmore preferably from 0.5 to 20 parts by weight, particularly preferablyfrom 1 to 15 parts by weight, and most preferably from 3 to 15 parts byweight or from 1 to 10 parts by weight. When the amount of the component(G2) is at least as large as the lower limit of the above-mentionedrange, the solubility of the resist film in an alkali developingsolution is likely to be increased. On the other hand, when the amountof the component (G2) is no more than the upper limit of theabove-mentioned range, an excellent sensitivity can be obtained.

In the present invention, the component (G) may include either thecomponent (G1) or the component (G2), but the component (G) consistingof a single component is preferably used.

Acid Generator Component; Component (G)

In the present invention, as the acid supply component (Z), an acidgenerator component which is decomposed by heat or light to act as anacid (hereafter, referred to as “component (B)”) can be used.

The component (B) is different from the compound (G), and generates anacid upon exposure in the step (2) or by baking (PEB) in the step (3).It is not necessary that the component (B) itself exhibits acidity.

When a prebake (PAB) is conducted after the step (1) and before theexposure in the step (2), the component (B) may generate an acid by theprebake. The prebake which is an arbitrary step will be described later.

As the component (B), there is no particular limitation, and any of theknown acid generators for use in conventional chemically amplifiedresist compositions can be used.

As the acid generators, a thermal-acid generator which generates an acidby heating, and a photo-acid generator which generates an acid uponexposure can be mentioned. Examples of these acid generators arenumerous, and include onium salt acid generators such as iodonium saltsand sulfonium salts; oximesulfonate acid generators; diazomethane-basedacid generators such as bisalkyl or bisaryl sulfonyl diazomethanes andpoly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate acid generators;iminosulfonate acid generators; and disulfone acid generators.

These acid generator components are known as photo-acid generators(PAG), but also have a function as thermal-acid generators (TAG).Therefore, as the acid generator component capable of using in thepresent invention, any acid generator can be appropriately selected fromthose which have been conventionally known as acid generators for use ina chemically amplified resist.

The “thermal-acid generator component which generates acid by heating”is a component which generates an acid by heating at a temperaturepreferably lower than a PEB temperature in the step (3), specifically,at a temperature of 200° C. or lower, preferably at a temperature of 50to 150° C. By virtue of using the thermal-acid generator which generatesan acid at a heating temperature equal to or lower than the PEBtemperature, the operation becomes easy. Moreover, it becomes easy tocontrol the generation of acid from the thermal-acid generator and thedeprotection reaction of the base component at different temperatures.By virtue of using a thermal-acid generator which preferably generatesacid at 50° C. or higher, the stability thereof in the resistcomposition becomes excellent.

As the onium salt acid generators of the component (B), an anion moietypreferably has at least one anion group selected from the groupconsisting of a sulfonate anion, a carboxylate anion, a sulfonylimideanion, a bis(alkylsulfonyl)imide anion and a tris(alkylsulfonyl)methideanion is preferable. Further, specific examples of the anion moietyinclude the same anion moiety as those described above for theaforementioned component (G1).

In addition, as the cation moiety, the cation moiety represented bygeneral formula (b-c1) or (b-c2) shown below can be mentioned.

In the formulas, each of R¹″ to R³″ and R⁵″ to R⁶″ independentlyrepresents an aryl group which may have a substituent, an alkyl group oran alkenyl group, wherein two of R¹″ to R³″ in formula (b-c1) may bebonded to each other to form a ring with the sulfur atom in the formula.

In formula (b-c1), each of R¹″ to R³″ independently represents an arylgroup which may have a substituent, an alkyl group or an alkenyl group.Two of R¹″ to R³″ may be mutually bonded to form a ring with the sulfuratom in the formula.

Examples of the aryl groups for R¹″ to R³″ include an unsubstituted arylgroup having 6 to 20 carbon atoms; and a substituted aryl group in whicha part or all of the hydrogen atoms of the aforementioned unsubstitutedaryl group has been substituted with alkyl groups, alkoxy groups,halogen atoms, hydroxyl groups, oxo groups (═O), aryl groups,alkoxyalkyloxy groups, alkoxycarbonylalkyloxy groups, —C(═O)—O—R⁶′,—O—C(═O)—R⁷′, —O—R⁸′ or the like. Each of R⁶′, R⁷′ and R⁸′ represents alinear or branched saturated hydrocarbon group of 1 to 25 carbon atoms,a cyclic saturated hydrocarbon group of 3 to 20 carbon atoms, or alinear or branched, aliphatic unsaturated hydrocarbon group of 2 to 5carbon atoms.

The unsubstituted aryl group for R¹″ to R³″ is preferably an aryl grouphaving 6 to 10 carbon atoms because it can be synthesized at a low cost.Specific examples thereof include a phenyl group and a naphthyl group.

The alkyl group as the substituent for the substituted aryl grouprepresented by R¹″ to R³″ is preferably an alkyl group having 1 to 5carbon atoms, and a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent for the substituted aryl group ispreferably an alkoxy group having 1 to 5 carbon atoms, and a methoxygroup, an ethoxy group, an n-propoxy group, an iso-propoxy group, ann-butoxy group or a tert-butoxy group is particularly desirable.

The halogen atom as the substituent for the substituted aryl group ispreferably a fluorine atom.

As the aryl group as the substituent for the substituted aryl group, thesame aryl groups as those described above for R¹″ to R³″ can bementioned.

Examples of alkoxyalkyloxy groups as the substituent for the substitutedaryl group include groups represented by a general formula shown below:

—O—C(R⁴⁷)(R⁴⁸)—O—R⁴⁹

In the formula, R⁴⁷ and R⁴⁸ each independently represents a hydrogenatom or a linear or branched alkyl group; and R⁴⁹ represents an alkylgroup.

The alkyl group for R⁴⁷ and R⁴⁸ preferably has 1 to 5 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is preferable that at least one of R⁴⁷ and R⁴⁸ be a hydrogen atom. Itis particularly desirable that at least one of R⁴⁷ and R⁴⁸ be a hydrogenatom, and the other be a hydrogen atom or a methyl group.

The alkyl group for R⁴⁹ preferably has 1 to 15 carbon atoms, and may belinear, branched or cyclic.

The linear or branched alkyl group for R⁴⁹ preferably has 1 to 5 carbonatoms. Examples thereof include a methyl group, an ethyl group, a propylgroup, an n-butyl group and a tert-butyl group.

The cyclic alkyl group for R⁴⁹ preferably has 4 to 15 carbon atoms, morepreferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbonatoms. Specific examples thereof include groups in which one or morehydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, and which may or may not be substituted with an alkylgroup of 1 to 5 carbon atoms, a fluorine atom or a fluorinated alkylgroup. Examples of the monocycloalkane include cyclopentane andcyclohexane. Examples of polycycloalkanes include adamantane,norbornane, isobornane, tricyclodecane and tetracyclododecane. Amongthese, a group in which one or more hydrogen atoms have been removedfrom adamantane is preferable.

Examples of the alkoxycarbonylalkyloxy group as the substituent for thesubstituted aryl group include groups represented by a general formulashown below:

—O—R⁵⁰—C(═O)—O—R⁵⁶

In the formula, R⁵⁰ represents a linear or branched alkylene group, andR⁵⁶ represents a tertiary alkyl group.

The linear or branched alkylene group for R⁵⁰ preferably has 1 to 5carbon atoms, and examples thereof include a methylene group, anethylene group, a trimethylene group, a tetramethylene group and a1,1-dimethylethylene group.

Examples of the tertiary alkyl group for R⁵⁶ include a2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropylgroup, a 1-(1-adamantyl)-1-methylbutyl group, a1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethylgroup, a 1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, a 1-(1-cyclohexyl)-1-methylpentylgroup, a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

Further, a group in which R⁵⁶ in the group represented by theaforementioned general formula: —O—R⁵⁰—C(═O)—O—R⁵⁶ has been substitutedwith R⁵⁶′ can also be mentioned. R⁵⁶′ represents a hydrogen atom, analkyl group, a fluorinated alkyl group or an aliphatic cyclic groupwhich may contain a hetero atom.

The alkyl group for R⁵⁶′ is the same as defined for the alkyl group forthe aforementioned R⁴⁹.

Examples of the fluorinated alkyl group for R⁵⁶′ include groups in whichpart or all of the hydrogen atoms within the alkyl group for R⁴⁹ hasbeen substituted with a fluorine atom.

Examples of the aliphatic cyclic group for R⁵⁶′ which may contain ahetero atom include an aliphatic cyclic group which does not contain ahetero atom, an aliphatic cyclic group containing a hetero atom in thering structure, and an aliphatic cyclic group in which a hydrogen atomhas been substituted with a hetero atom.

As an aliphatic cyclic group for R⁵⁶′ which does not contain a heteroatom, a group in which one or more hydrogen atoms have been removed froma monocycloalkane or a polycycloalkane such as a bicycloalkane, atricycloalkane or a tetracycloalkane can be mentioned. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

Specific examples of the aliphatic cyclic group for R⁵⁶′ containing ahetero atom in the ring structure include groups represented by formulas(L1) to (L6) and (S1) to (S4) described above.

As the aliphatic cyclic group for R⁵⁶′ in which a hydrogen atom has beensubstituted with a hetero atom, an aliphatic cyclic group in which ahydrogen atom has been substituted with an oxygen atom (═O) can bementioned.

Each of R⁶′, R⁷′ and R⁸′ in —C(═O)—O—R⁶′, —O—C(═O)—R⁷′, —O—R⁸′represents a linear or branched saturated hydrocarbon group of 1 to 25carbon atoms, a cyclic saturated hydrocarbon group of 3 to 20 carbonatoms, or a linear or branched, aliphatic unsaturated hydrocarbon groupof 2 to 5 carbon atoms.

The linear or branched, saturated hydrocarbon group has 1 to 25 carbonatoms, preferably 1 to 15 carbon atoms, and more preferably 4 to 10carbon atoms.

Examples of the linear, saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group and a decylgroup.

Examples of the branched saturated hydrocarbon group include a1-methylethyl group, 1-methylpropyl group, 2-methylpropyl group,1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group,1-ethylbutyl group, 2-ethylbutyl group, 1-methylpentyl group,2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group,tert-butyl group, tert-pentyl group and tert-hexyl group.

The linear or branched, saturated hydrocarbon group may have asubstituent. Examples of the substituent include an alkoxy group, ahalogen atom, a halogenated alkyl group, a hydroxyl group, an oxygenatom (═O), a cyano group and a carboxy group.

The alkoxy group as the substituent for the linear or branched saturatedhydrocarbon group is preferably an alkoxy group having 1 to 5 carbonatoms, more preferably a methoxy group, an ethoxy group, an n-propoxygroup, an iso-propoxy group, an n-butoxy group or a tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the linear orbranched, saturated alkyl group include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Examples of the halogenated alkyl group as the substituent for thelinear or branched, saturated hydrocarbon group include a group in whichpart or all of the hydrogen atoms within the aforementioned linear orbranched, saturated hydrocarbon group have been substituted with theaforementioned halogen atoms.

The cyclic saturated hydrocarbon group of 3 to 20 carbon atoms for R⁶′,R⁷′ and R⁸′ may be either a polycyclic group or a monocyclic group, andexamples thereof include groups in which one hydrogen atom has beenremoved from a monocycloalkane, and groups in which one hydrogen atomhas been removed from a polycycloalkane (e.g., a bicycloalkane, atricycloalkane or a tetracycloalkane). More specific examples includegroups in which one hydrogen atom has been removed from amonocycloalkane such as cyclopentane, cyclohexane, cycloheptane orcyclooctane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

Further, examples of the cyclic saturated hydrocarbon group of 3 to 20carbon atoms include the same cyclic saturated hydrocarbon groups asthose described above for the aforementioned tertiary alkyl groups ofR⁵⁶.

The cyclic, saturated hydrocarbon group may have a substituent. Forexample, part of the carbon atoms constituting the ring within thecyclic alkyl group may be substituted with a hetero atom, or a hydrogenatom bonded to the ring within the cyclic alkyl group may be substitutedwith a substituent.

In the former example, a heterocycloalkane in which part of the carbonatoms constituting the ring within the aforementioned monocycloalkane orpolycycloalkane has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom, and one or more hydrogenatoms have been removed therefrom, can be used. Further, the ring maycontain an ester bond (—C(═O)—O—). More specific examples include alactone-containing monocyclic group, such as a group in which onehydrogen atom has been removed from γ-butyrolactone; and alactone-containing polycyclic group, such as a group in which onehydrogen atom has been removed from a bicycloalkane, tricycloalkane ortetracycloalkane containing a lactone ring.

In the latter example, as the substituent, the same substituent groupsas those for the aforementioned linear or branched alkyl group, or alower (1 to 5 carbon atoms) alkyl group can be used.

Alternatively, R⁶′, R⁷′ and R⁸′ may be a combination of a linear orbranched alkyl group and a cyclic group.

Examples of the combination of a linear or branched alkyl group with acyclic alkyl group include groups in which a cyclic alkyl group as asubstituent is bonded to a linear or branched alkyl group, and groups inwhich a linear or branched alkyl group as a substituent is bonded to acyclic alkyl group.

Examples of the linear aliphatic unsaturated hydrocarbon group for R⁶′,R⁷′ and

R⁸′ include a vinyl group, a propenyl group (an allyl group) and abutynyl group.

Examples of the branched aliphatic unsaturated hydrocarbon group forR⁶′, R⁷′ and R⁸′ include a 1-methylpropenyl group and a 2-methylpropenylgroup.

The aforementioned linear or branched, aliphatic unsaturated hydrocarbongroup may have a substituent. Examples of the substituents include thesame substituents as those which the aforementioned linear or branchedalkyl group may have.

Among the aforementioned examples, as R⁷′ and R⁸′, in terms ofimprovement in lithography properties and shape of the resist pattern, alinear or branched, saturated hydrocarbon group of 1 to 15 carbon atomsor a cyclic saturated hydrocarbon group of 3 to 20 carbon atoms ispreferable.

Examples of the alkyl group for R¹″ to R³″ include linear, branched orcyclic alkyl groups of 1 to 10 carbon atoms. Among these, alkyl groupsof 1 to 5 carbon atoms are preferable as the resolution becomesexcellent. Specific examples thereof include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, acyclohexyl group, a nonyl group, and a decyl group, and a methyl groupis most preferable because it is excellent in resolution and can besynthesized at a low cost.

The alkenyl group for R¹″ to R³″ preferably has 2 to 10 carbon atoms,more preferably 2 to 5 carbon atoms, and still more preferably 2 to 4carbon atoms. Specific examples thereof include a vinyl group, apropenyl group (an allyl group), a butynyl group, a 1-methylpropenylgroup and a 2-methylpropenyl group.

When two of R¹″ to R³″ are bonded to each other to form a ring with thesulfur atom in the formula, it is preferable that the two of R¹″ to R³″form a 3 to 10-membered ring including the sulfur atom, and it isparticularly desirable that the two of R¹″ to R³″ form a 5 to 7-memberedring including the sulfur atom.

Specific examples of the preferred cation moiety for the compoundrepresented by the above formula (b-c1) include cation moieties shownbelow.

In the formula, g1 represents a recurring number, and is an integer of 1to 5.

In the formula, g2 and g3 represent recurring numbers, wherein g2 is aninteger of 0 to 20, and g3 is an integer of 0 to 20.

In the formulas, R^(c) is the same as the substituents described abovein relation to the substituted aryl group (i.e., an alkyl group, analkoxy group, an alkoxyalkyloxy group, an alkoxycarbonylalkyloxy group,a halogen atom, a hydroxyl group, an oxo group (═O), an aryl group,—C(═O)—O—R⁶′, —O—C(═O)—R⁷′ and —O—R⁸′).

In formula (b-c2) above, each of R⁵″ and R⁶″ independently represents anaryl group which may have a substituent, an alkyl group or an alkenylgroup.

As the aryl group for R⁵″ and R⁶″, the same aryl groups as thosedescribed above for R¹″ to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same alkyl groups as thosedescribed above for R¹″ to R³″ can be used.

As the alkenyl group for R⁵″ and R⁶″, the same alkenyl groups as thosedescribed above for R¹″ to R³″ can be used.

Specific examples of the cation moiety of the compound represented bythe above general formula (b-c2) include diphenyliodonium andbis(4-tert-butylphenyl)iodonium.

In the present description, an oxime sulfonate-based acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation(exposure). Such oxime sulfonate-based acid generators are widely usedfor a chemically amplified resist composition, and can be appropriatelyselected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly desirable. In other words, the halogenatedalkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, a partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,an aryl group, or a cyano group is preferable. Examples of the alkylgroup and the aryl group for R³² include the same alkyl groups and arylgroups as those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate-based acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate-based acid generatorsinclude α-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate-based acid generators disclosed in WO 2004/074242A2(Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane-based acid generators, specificexamples of suitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may also be used favorably.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

When the resist composition of the present invention includes thecomponent (B), as the component (B), one type of the aforementioned acidgenerator may be used, or two or more types may be used in combination.

In the case where the resist composition of the present inventioncontains the component (B), when the component (B) is a thermal-acidgenerator, the amount of the component (B) relative to 100 parts byweight of the component (A) is preferably 0.5 to 30 parts by weight, andmore preferably 1 to 20 parts by weight. When the component (B) is aphoto-acid generator, the amount of the component (B) relative to 100parts by weight of the component (A) is preferably 0.5 to 30 parts byweight, and more preferably 1 to 20 parts by weight. When the amount ofthe component (B) is within the above-mentioned range, formation of aresist pattern can be satisfactorily performed. In addition, when theamount of the component (B) is at least as large as the lower limit ofthe above-mentioned range, solubility of the resist film in thedeveloping solution is likely to increase and resolution is enhanced. Onthe other hand, when the amount is no more than the upper limit of theabove-mentioned range, sensitivity becomes excellent. In addition, inthe case of the photo-acid generator, when the amount is no more thanthe upper limit of the above-mentioned range, the transparency of theresist film becomes excellent.

In the case where the resist composition of the present inventioncontains the component (B), the amount of the component (B) relative tothe combined total amount of the component (G) and component (B) ispreferably 50% by weight or less, and more preferably 20% by weight orless.

Compound (F); Component (F)

In the present invention, a compound (F) is a compound containing atleast one selected from the group consisting of a fluorine atom and asilicon atom and containing no acid decomposable group which exhibitsincreased polarity by the action of acid.

Examples of the “acid decomposable group which exhibits increasedpolarity by the action of acid” includes the same as those describedabove for the “acid decomposable groups which exhibit increased polarityby the action of an acid” of the aforementioned structural unit (a1).

The component (F) may be a low molecular weight compound, polymer ormixture thereof. Similarly to the description of the aforementionedcomponent (A), the “low molecular weight compound” refers to anon-polymer having a molecular weight in the range of 500 to less than4,000. The “polymer” in the component (F) refers to a product generatedby bonding 2 or more single unit compound molecules to each other. Asthe molecular weight of the polymer, the weight average molecular weightin terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC) is used.

When the component (F) is the polymer, a structural unit constitutingthe component (F) is not particularly limited, and a structural unitderived from a compound having the ethylenic double bond.

A “structural unit derived from a compound having the ethylenic doublebond” refers to a structural unit having a structure in which a singlebond is formed by the cleavage of the ethylenic double bond in thecompound containing the ethylenic double bond.

Examples of the compound containing the ethylenic double bond include anacrylic acid which may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent, or an ester thereof,an acrylamide which may have the hydrogen atom bonded to the carbon atomon the α-position substituted with a substituent, or derivative thereof,a vinyl cyclic compound which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent, acycloolefin or derivative thereof, and a vinyl sulfonate ester.

Of these, an acrylic acid which may have the hydrogen atom bonded to thecarbon atom on the α-position substituted with a substituent, or anacrylate ester, and a vinyl cyclic compound which may have the hydrogenatom bonded to the carbon atom on the α-position substituted with asubstituent are preferable.

Each of an “acrylate ester” and a substituent bonded to the carbon atomon the α-position is the same as described above.

In the component (F), it is preferable that a hydrogen atom, an alkylgroup of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5carbon atoms is bonded to the carbon atom on the α-position of the(α-substituted) acrylic acid or ester thereof, a hydrogen atom, an alkylgroup of 1 to 5 carbon atoms or a fluorinated alkyl group of 1 to 5carbon atoms is more preferable, and in terms of industrialavailability, a hydrogen atom or a methyl group is the most desirable.

An “organic group” refers to a group containing a carbon atom, and mayinclude atoms other than carbon atoms (e.g., a hydrogen atom, an oxygenatom, a nitrogen atom, a sulfur atom, a halogen atom (such as a fluorineatom and a chlorine atom) and the like).

The organic group contained in the (α-substituted) acrylate ester is notparticularly limited, and an example thereof includes a characteristicgroup such as an aromatic group (a group in which one or more hydrogenatoms have been removed from an aromatic compound), a polarityconversion group (a group decomposed by the action of a base andgenerating a polar group; examples of the polar group include a carboxygroup, a hydroxy group and an amino group) and the aforementioned aciddecomposable group, and a characteristic group-containing groupcontaining any one of these characteristic groups in the structurethereof. An example of the characteristic group-containing groupincludes a group in which a divalent linking group is bonded to thecharacteristic group. As the divalent linking group, the same divalentlinking groups as those described for Y² in the aforementioned generalformula (a1-0-2) can be mentioned.

Examples of the “acrylamide or derivative thereof” include an acrylamide(hereinafter, sometimes referred to as a “(α-substituted) acrylamide”)which may have the hydrogen atom bonded to the carbon atom on theα-position substituted with a substituent, and a compound in whicheither or both of the terminal hydrogen atoms of an amino group of the(α-substituted) acrylamide has been substituted with a substituent.

Examples of the substituent which may be bonded to the carbon atom onthe α-position of the acrylamide or derivative thereof include the sameas those described above for the substituent bonded to the carbon atomon the α-position of the (α-substituted) acrylate ester.

As the substituent for substituting either or both of the terminalhydrogen atoms of an amino group of the (α-substituted) acrylamide, anorganic group is preferable. The organic group is not particularlylimited, and examples thereof include the same organic group as thosedescribed above for the organic group contained in the aforementioned(α-substituted) acrylate ester.

As examples of the compound in which either or both of the terminalhydrogen atoms of an amino group of the (α-substituted) acrylamide hasbeen substituted with a substituent, a compound in which —C(═O)—O—bonded to the carbon atom on the α-position of the (α-substituted)acrylate ester is substituted with —C(═O)—N(R^(b))— [wherein R^(b)represents a hydrogen atom or an alkyl group of 1 to 5 carbon atoms] canbe mentioned.

In the formula, the alkyl group for R^(b) is preferably linear orbranched.

A “vinyl cyclic compound” refers to a compound having a ring structureof an aromatic compound or an alicyclic compound, and one or more vinylgroups bonded directly or via a divalent linking group to the ringstructure.

Examples of the aromatic compound include benzene and naphthalene.

The alicyclic compound may be either a monocyclic compound or apolycyclic compound. The monocyclic compound is preferablymonocycloalkane, and examples thereof include cyclopentane andcyclohexane. The polycyclic compound is preferably polycycloalkane, andexamples thereof include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane.

Examples of the divalent linking group include —O—, —N— and —S—.

Examples of the substituent which may be bonded to the carbon atom (acarbon atom bonded to the ring structure or the linking group within thecarbon atoms of the vinyl group) on the α-position of the vinyl cycliccompound include the same as those described above for the substituentbonded to the carbon atom on the α-position of the (α-substituted)acrylate ester.

Hereafter, the vinyl cyclic compound which may have the hydrogen atombonded to the carbon atom on the α-position substituted with asubstituent is sometimes referred to as a “(α-substituted) vinyl cycliccompound”.

Specific examples of the structural unit derived from the(α-substituted) acrylic acid or ester thereof include a structural unitrepresented by general formula (U-1) shown below.

Specific examples of the structural unit derived from the(α-substituted) acrylamide or derivative thereof include a structuralunit represented by general formula (U-2) shown below.

Specific examples of the structural unit derived from the(α-substituted) vinyl cyclic compound include a structural unitrepresented by any one of general formulas (U-3) to (U-5) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X^(a)to X^(d) each independently represents a hydrogen atom or an organicgroup; R^(b) represents a hydrogen atom or an alkyl group of 1 to 5carbon atoms; R^(c), R^(d) and R^(g) each independently represents ahalogen atom, —COOX^(e) (wherein, X^(e) represents a hydrogen atom or anorganic group), an alkyl group of 1 to 5 carbon atoms or a halogenatedalkyl group of 1 to 5 carbon atoms; X^(g) represents a divalent linkinggroup; R^(e) represents a group which forms an aliphatic monocyclicgroup with the carbon atom to which R^(e) is bonded; px represents aninteger of 0 to 3, and qx represents an integer of 0 to 5, provided thatpx+qx ═0 to 5; when qx is an integer of 2 or more, the plurality ofR^(c) may be the same or different from each other; x represents aninteger of 0 to 3; y represents an integer of 0 to 3; and z representsan integer of 0 to 4, provide that x+y+z=0 to 7; when y+z is an integerof 2 or more, the plurality of R^(d) may be the same or different fromeach other; and rx represents an integer of 0 to 5, when rx is aninteger of 2 or more, the plurality of R⁹ may be the same or differentfrom each other.

When the component (F) is the low molecular weight compound, thecomponent (F) is preferably a compound having a polymerizable group. A“polymerizable group” refers to a group enabling the compound having thepolymerizable group to polymerize by radical polymerization or the like,and refers to a group including a multiple bond among carbon atoms, forexample, such as an ethylenic double bond.

The compound having a polymerizable group is preferably the lowmolecular weight compound having an ethylenic double bond, and mostpreferably an acrylic acid which may have the hydrogen atom bonded tothe carbon atom on the α-position substituted with a substituent, or anester thereof. Specifically, preferable examples thereof includemonomers providing structural units represented by the aforementionedgeneral formulas (U-1) to (U-5), respectively.

Preferable example of the component (F) according to the presentinvention include a polymer having a structural unit containing at leastone selected from the group consisting of a fluorine atom and a siliconatom and containing no acid decomposable group which exhibits increasedpolarity by the action of acid within the structural unit represented byany one of general formulas (U-1) to (U-5), or a monomer providing thestructural unit.

In the resist composition of the present invention, the component (F) ispreferably a polymer (hereafter, referred to as “polymer (F1)” or“component (F1)”) having a structural unit (hereafter, referred to as“structural unit (f1)”) represented by general formula (f1-1) describedlater.

Further, the component (F) is also preferably a compound (hereafter,referred to as “compound (F11)” or “component (F11)”) represented bygeneral formula (f11-1) described later.

Here, any of the component (F) contains no acid decomposable group whichexhibits increased polarity by the action of acid.

Polymer (F1)

The component (F1) is a polymer containing the structural unit (f1) andcontaining no acid decomposable group which exhibits increased polarityby the action of acid.

[Structural Unit (f1)]

The structural unit (f1) is a structural unit represented by generalformula (f1-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Arepresents —O— or —NH—; X₀ represents a single bond or a divalentlinking group; R₀ represents an organic group; at least one of X₀ and R₀contains a fluorine atom or a silicon atom; and v is 0 or 1.

In general formula (f1-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms. As the alkyl group of 1 to 5 carbon atoms or the halogenatedalkyl group of 1 to 5 carbon atoms for R, the same as those describedabove for the alkyl group of 1 to 5 carbon atoms or the halogenatedalkyl group of 1 to 5 carbon atoms in the aforementioned substituentbonded to the carbon atom on the α-position. Of these, R is preferably ahydrogen atom or a methyl group.

In general formula (f1-1), A represents O (oxygen atom) or NH, and ispreferably O (oxygen atom).

In general formula (f1-1), v represents 0 or 1. “v is 0” means that—C(═O)-A- in the formula is replaced with a single bond.

In general formula (f1-1), X₀ represents a single bond or a divalentlinking group.

Examples of the divalent linking group for X₀ include divalenthydrocarbon groups which may have a substituent and divalent linkinggroups containing a hetero atom, and the same divalent hydrocarbongroups which may have a substituent and divalent linking groupscontaining a hetero atom as those defined above for Y² in generalformula (a1-0-2) can be used, provided that the divalent linking groupfor X₀ includes no acid decomposable group in the structure thereof. Asan example of the acid decomposable group, the same as those describedabove for “acid decomposable groups which exhibit increased polarity bythe action of an acid” of the aforementioned structural unit (a1) can bementioned.

As X₀, a single bond or a divalent linking group containing a heteroatom is preferable, and more preferably a single bond, a divalentlinking group containing —C(═O)—O— or a divalent linking groupcontaining —O—.

When v represents 0, preferable examples of the divalent linking groupfor X₀ include a divalent aromatic hydrocarbon group which may have asubstituent, a combination of a divalent aromatic hydrocarbon groupwhich may have a substituent with a divalent linking group containing—O—C(═O)—, a divalent alicyclic group which may have a substituent and acombination of a divalent alicyclic group which may have a substituentwith a divalent linking group containing —O—.

Specifically, a group in which an additional one hydrogen atom has beenremoved from a phenyl group or a naphthyl group which may have asubstituent, a combination of a group in which an additional onehydrogen atom has been removed from a phenyl group or a naphthyl groupwhich may have a substituent with —O—C(═O)—, a combination of a group inwhich an additional one hydrogen atom has been removed from a phenylgroup or a naphthyl group which may have a substituent, —O—C(═O)— and alinear alkylene group, a group in which two hydrogen atoms have beenremoved from a cycloalkane which may have a substituent, and acombination of a group in which two hydrogen atoms have been removedfrom a cycloalkane which may have a substituent with —O— areparticularly desirable.

Further, when v represents 1, as the divalent linking group for X₀, acombination of a divalent hydrocarbon group which may have a substituentwith a divalent linking group containing —C(═O)—O—, a combination of adivalent aromatic hydrocarbon group which may have a substituent with adivalent linking group containing —O—, and a combination of a divalentchain-like hydrocarbon group which may have a substituent with adivalent linking group containing —O—C(═O)— are preferable, and morepreferably a combination of a divalent chain-like hydrocarbon group or adivalent aromatic hydrocarbon group which may have a substituent with—C(═O)—O—, a combination of a divalent chain-like hydrocarbon group or adivalent aromatic hydrocarbon group which may have a substituent with—O—C(═O)—, a combination of a divalent aromatic hydrocarbon group whichmay have a substituent, —O— and a divalent chain-like hydrocarbon groupwhich may have a substituent, and a combination of a divalent chain-likehydrocarbon group which may have a substituent, —O—C(═O)— and a divalentchain-like hydrocarbon group which may have a substituent.

When X₀ is a divalent linking group, X₀ may or may not have a fluorineatom or a silicon atom. When X₀ is a single bond, or when the divalentlinking group for X₀ has no fluorine atom nor a silicon atom, an organicgroup for R₀ described later has a fluorine atom or a silicon atom.

In general formula (f1-1), R₀ represents an organic group.

The organic group for R₀ may be an organic group which has a fluorineatom or a silicon atom, or an organic group which has no fluorine atomnor a silicon atom, but when X₀ is a single bond, or when the divalentlinking group for X₀ has no fluorine atom nor a silicon atom, theorganic group for R₀ has a fluorine atom or a silicon atom.

Here, an “organic group which has a fluorine atom or a silicon atom”refers to a group in which part or all of the hydrogen atoms of theorganic group has been substituted with a fluorine atom or a siliconatom.

Preferable examples of the organic group for R₀ include a hydrocarbongroup which may have a fluorine atom or a silicon atom. The hydrocarbongroup which may have a fluorine atom or a silicon atom may be either analiphatic hydrocarbon group or an aromatic hydrocarbon group.

As the aliphatic hydrocarbon group for R₀, a linear, branched or cyclicalkyl group can be used.

The linear or branched alkyl group preferably has 1 to 15 carbon atoms,more preferably 1 to 10, still more preferably 1 to 8, and mostpreferably 1 to 5.

The cyclic alkyl group (alicyclic group) preferably has 4 to 15 carbonatoms, more preferably 4 to 10 carbon atoms, still more preferably 6 to10 carbon atoms, and most preferably 5 to 7 carbon atoms.

The aromatic hydrocarbon group for R₀ preferably has 5 to 30 carbonatoms, more preferably 5 to 20, still more preferably 6 to 15, and mostpreferably 6 to 12. It is particularly desirable that the aromatichydrocarbon group for R₀ be a phenyl group or a naphthyl group.

In these alkyl groups and aromatic hydrocarbon groups, it is preferablethat a hydrogen atom therein be substituted with a fluorine atom or asilicon atom, 25% or more hydrogen atoms within the alkyl group and thearomatic hydrocarbon group are preferably substituted with a fluorineatom or a silicon atom, more preferably 50% or more hydrogen atomstherein are substituted with a fluorine atom or a silicon atom. Allhydrogen atoms therein may be substituted with a fluorine atom or asilicon atom.

Further, in these alkyl groups and aromatic hydrocarbon groups, ahydrogen atom therein may be substituted with a substituent other than afluorine atom or a silicon atom. Examples of the substituent other thana fluorine atom or a silicon atom include a hydroxyl group, a chlorineatom, a bromine atom, an iodine atom, an alkoxy group having 1 to 5carbon atoms, and a fluorinated alkoxy group having 1 to 5 carbon atoms.Furthermore, in the cyclic alkyl group and the aromatic hydrocarbongroup, a hydrogen atom therein may be substituted with an alkyl group of1 to 5 carbon atoms. The alkyl group of 1 to 5 carbon atoms may belinear or branched, and is the same alkyl group of 1 to 5 carbon atomsas described above for the substituent on the α-position.

Specific examples of preferred structural unit (f1) represented bygeneral formula (f1-1) and containing a fluorine atom include structuralunits represented by general formulas (f1-11) to (f1-15) shown below.

In the formulas, each of Rf¹, Rf² and Rf⁵ represents an organic groupcontaining a fluorine atom; X₀ represents a single bond or a divalentlinking group; A is the same as defined above; each of X⁰¹ to X⁰²represents a divalent linking group; each of Rf³ to Rf⁴ represents anorganic group which may contain a fluorine atom; and at least one of X⁰¹and Rf³, and at least one of X⁰² and Rf⁴ contains a fluorine atom.

In general formula (f1-11), Rf¹ represents an organic group containing afluorine atom, and is preferably an aromatic hydrocarbon groupcontaining a fluorine atom, a combination of an alkyl group in whichhydrogen atoms therein are substituted with a fluorine atom and ahydroxyl group, and an aromatic hydrocarbon group which may contain afluorine atom, and a combination of an alkyl group in which hydrogenatoms therein are substituted with a fluorine atom and a fluorinatedalkoxy group having 1 to 5 carbon atoms, and an aromatic hydrocarbongroup.

Examples of the aromatic hydrocarbon group containing a fluorine atominclude an aromatic hydrocarbon group in which part or all of thehydrogen atoms thereof are substituted with fluorine atoms among thearomatic hydrocarbon group for aforementioned R₀.

In general formula (f1-12), X₀ represents a single bond or a divalentlinking group, and is the same as the aforementioned X₀.

Rf⁵ represents an organic group containing a fluorine atom, and ispreferably a chain-like alkyl group in which hydrogen atoms therein aresubstituted with a fluorine atom and a hydroxyl group, and a combinationof an alkyl group in which hydrogen atoms therein are substituted with afluorine atom and a hydroxyl group, with a cyclic alkyl group.

As the chain-like alkyl group and the cyclic alkyl group, the same asthose described above for the aliphatic hydrocarbon group (linear,branched, or cyclic alkyl group) in the aforementioned R₀ can be given.

In general formula (f1-13), A is the same as defined above.

Rf² represents an organic group containing a fluorine atom, and ispreferably a chain-like alkyl group containing a fluorine atom, a cyclicalkyl group containing a fluorine atom, an aromatic hydrocarbon groupcontaining a fluorine atom, a chain-like alkyl group in which hydrogenatoms therein are substituted with a fluorine atom and a hydroxyl group,an aromatic hydrocarbon group in which hydrogen atoms therein aresubstituted with a fluorine atom and a hydroxyl group, or a combinationof an alkyl group in which hydrogen atoms therein are substituted with afluorine atom with a cyclic alkyl group.

As the cyclic alkyl group containing a fluorine atom and the aromatichydrocarbon group containing a fluorine atom, a cyclic alkyl group and aaromatic hydrocarbon group in which part or all of the hydrogen atomsthereof have been substituted with a fluorine atom among the cyclicalkyl group and the aromatic hydrocarbon group in the aforementioned R₀can be mentioned.

In general formula (f1-14), X⁰¹ represents a divalent linking group. Asan example thereof, the same as those described above for the divalentlinking group in the aforementioned X₀ can be mentioned.

Among these, X⁰¹ is preferably a divalent aromatic hydrocarbon groupwhich may have a substituent, and most preferably a group in which anadditional one hydrogen atom has been removed from a phenyl group or anaphthyl group which may have a substituent.

The substituent is preferably a fluorine atom or an alkoxy group having1 to 5 carbon atoms. When X⁰¹ has no fluorine atom, Rf³ has a fluorineatom.

In general formula (f1-14), Rf³ represents an organic group which maycontain a fluorine atom. As an example thereof, the same organic groupas those described above for the aforementioned R₀ can be used. Rf³ ispreferably a linear or branched alkyl group which may contain a fluorineatom, and the linear or branched alkyl group which may contain afluorine atom preferably has 1 to 5 carbon atoms.

In general formula (f1-15), A is the same as defined above.

X⁰² represents a divalent linking group. As an example thereof, the sameas those described above for the divalent linking group in theaforementioned X₀ can be mentioned.

Among these, X⁰² is preferably a divalent aliphatic hydrocarbon groupwhich may have a substituent, a divalent aromatic hydrocarbon groupwhich may have a substituent, an ether bond (—O—), an ester bond(—C(═O)—O—, —O—C(═O)—), or a combination thereof.

The substituent is preferably a fluorine atom or an alkoxy group having1 to 5 carbon atoms.

Each of the divalent aliphatic hydrocarbon group and the divalentaromatic hydrocarbon group for X⁰² may have a carbon atom constitutingthe hydrocarbon group substituted with an oxygen atom or a nitrogenatom.

When X⁰² has no fluorine atom, Rf⁴ has a fluorine atom.

In general formula (f1-15), Rf⁴ represents an organic group which maycontain a fluorine atom, and is the same as the aforementioned Rf³.

In the present invention, if resist patterns are formed by an alkalidevelopment using the resist composition including the polymer (F1), Rf⁴in general formula (f1-15) is preferably a base dissociable group. It ispreferable that Rf⁴ be a base dissociable group, because the basedissociable group for Rf⁴ is decomposed by the alkali development in thestep (4) to enhance the hydrophilicity of the resist film. Rf⁴ which isthe base dissociable group is not particularly limited as long as Rf⁴ isa hydrocarbon group or a hydrocarbon group which may have a substituent.It is preferable that Rf⁴ have a fluorine atom.

The term “base dissociable group” describes a group that dissociates(i.e., —O—Rf⁴ is dissociated) under the action of an alkali developingsolution. The expression “dissociate in an alkali developing solution”means that the group is dissociated under the action of an alkalideveloping solution (and is preferably dissociated under the action of a2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH)at 23° C.), and exhibits increased solubility in an alkali developingsolution. This is because under the action of a base (an alkalideveloping solution), an ester bond [—C(═O)—O—Rf⁴] dissociates(hydrolyzes), thereby forming a hydrophilic group [—C(═O)—OH] (i.e.,—O—Rf⁴ is dissociated).

In this manner, since a terminal of the structural unit in the polymer(F1) changes from being hydrophobic before to hydrophilic after thedevelopment, hydrophilicity of the component (F1) is enhanced in thealkali development. Therefore, the effect of improving developmentdefects becomes excellent. Further, in the immersion exposure, scantracking ability is enhanced during the immersion exposure and defectsor the like after exposure is reduced. Accordingly, the polymer (F1)having the structural unit containing the base dissociable group isuseful not only in a resist composition for a dry exposure but also in aresist composition for an immersion exposure.

Specific examples of structural units represented by general formulas(f1-11) to (f1-15) are shown below. In the formulas, R^(β) represents ahydrogen atom or a methyl group.

The structural unit (f1) containing a fluorine atom is preferably atleast one selected from the group consisting of a structural unitrepresented by any one of formulas (f1-11) to (f1-15).

Of these, since an enhanced water repellency effect on the surface of aresist film can be achieved, a structural unit represented by formula(f1-13) or (f1-15) is more preferable, and most preferably a structuralunit represented by formula (f1-15).

Among the structural unit (f1) represented by formula (f1-1), specificexamples of preferred the structural unit (f1) contains a silicon atominclude a silicon-containing structural unit in which R₀ in theaforementioned formula (f1-1) is an organic group containing atrialkylsilyl group or a siloxane bond. Here, the silicon-containingstructural unit includes no acid decomposable group which exhibitincreased polarity by the action of an acid.

As an example of the trialkylsilyl group, a group represented by formula—Si(R⁷⁴)(R⁷⁵)(R⁷⁶) can be mentioned. In the formula, R⁷⁴ to R⁷⁶ eachindependently represent a linear or branched alkyl group. The alkylgroup preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and still more preferably 1 to 5 carbon atoms. The alkyl group ispreferably a methyl group, an ethyl group, an isopropyl group, a t-butylgroup and the like, and a methyl group is particularly desirable.

Specific examples of the trialkylsilyl group include a trimethylsilylgroup, a triethylsilyl group, a triisopropylsilyl group, and at-butyldimethylsilyl group.

The organic group containing the trialkylsilyl group may be constitutedof only a trialkylsilyl group, or may be a group in which n (nrepresents an integer of 1 or more) trialkylsilyl groups are bonded to a(n+1)-valent linking group. Among (n+1)-valent linking groups, examplesof a linking group wherein n is 1, that is, a divalent linking group,include a divalent hydrocarbon group which may have a substituent and adivalent linking group containing a hetero atom, and the same divalenthydrocarbon groups which may have a substituent and divalent linkinggroups containing a hetero atom as those defined above for Y² in generalformula (a1-0-2) can be used, provided that the divalent linking groupfor X₀ includes no acid decomposable group in the structure thereof.Such a divalent linking group is preferably a linear or branchedalkylene group in which an ether bond or an ester bond may be inserted.As examples of a linking group wherein n represents 2 or more, a groupin which (n-1) additional hydrogen atoms have been removed from thelinking group within the divalent linking group can be mentioned.

Examples of the organic group containing a siloxane bond (Si—O—Si)include a cyclic siloxane in which a hydrocarbon group is bonded to asilicon atom, a polyhedral oligomeric silsesquioxane in which ahydrocarbon group is bonded to a silicon atom, and a group in which partof a carbon chain within a chain-like or cyclic alkyl group issubstituted with —Si—O—Si—. The hydrocarbon group bonded to a siliconatom within the cyclic siloxane or the polyhedral oligomericsilsesquioxane may be an aliphatic hydrocarbon group or an aromaticgroup. The hydrocarbon group is preferably an aliphatic group, and morepreferably an alkyl group of 1 to 5 carbon atoms.

As the structural unit (f1) containing a silicon atom, it is preferablethat v is 1 and X₀ is a divalent linking group in formula (f1-1), or vis 0 and X₀ is a single bond in formula (f1-1).

In the polymer (F1), as the structural unit (f1), one type may be usedalone, or two or more types may be used in combination.

In the polymer (F1), the amount of the structural unit (f1) based on thecombined total amount of all structural units constituting the polymer(F1) is preferably 10 mol % or more, more preferably 30 mol % or more,still more preferably 50 mol % or more, and may even be 100 mol % (i.e.,homopolymer). When the amount of the structural unit (f1) is at least aslarge as the lower limit of the above-mentioned range, in formation of aresist pattern, it is possible that surface of a resist filmsatisfactorily becomes water repellency and excellent resist patternsare formed in the immersion exposure.

When the polymer (F1) includes a structural unit other than thestructural unit (f1), the amount of the structural unit (f1) ispreferably 95 mol % or less, and more preferably 85 mol % or less.

[Other Structural Units]

The polymer (F1) may also have a structural unit other than thestructural unit (f1), depending on an application, as long as theeffects of the present invention are not impaired.

As the other structural unit, any structural unit which iscopolymerizable with the structural unit (f1) can be used without anyparticular limitation, and any of the multitude of conventionalstructural units used within resist resins for ArF excimer lasers, KrFexcimer lasers, EB or EUV can be used. Examples of the other structuralunit include the same as those of the structural units (a0), (a2) to(a6) in the aforementioned component (A). Among these, a structural unitwhich does not contain a fluorine atom, a silicon atom or an aciddecomposable group may be appropriately selected for use.

Among the aforementioned examples, the component (F1) is preferably apolymer including the structural unit (f1), more preferably ahomopolymer composed of the repeated structure of the structural unit(f1), and most preferably a homopolymer composed of the repeatedstructure of the structural unit (f1) containing a fluorine atom. Insuch a case, the homopolymer may be composed of the repeated structureof the single structural unit (f1), or may be composed of the repeatedstructure of two or more types. The homopolymer is preferably composedof the repeated structure of the single structural unit (f1).

As another aspect of the component (F), for example, afluorine-containing polymeric compound described in Japanese UnexaminedPatent Application, First Publication No. 2010-002870 can be used.

As specific examples of another aspect of the component (F), a polymerhaving a structural unit (f1-1B) represented by general formula (f1-1B)shown below can be used. The polymer is preferably a polymer(homopolymer) consisting of a structural unit (f1-1B) shown below; acopolymer of a structural unit represented by formula (f1-1B) shownbelow and the aforementioned structural unit (a1); or a copolymer of astructural unit represented by formula (f1-1B) shown below, a structuralunit derived from acrylic acid or methacrylic acid and theaforementioned structural unit (a1). As the structural unit (a1) to becopolymerized with a structural unit represented by the formula (f1-1B)shown below, a structural unit represented by the formulas (a1-0-11) to(a1-0-13) is preferable, and a structural unit represented by theformula (a1-1-32) is particularly desirable.

In the formula, R is the same as defined above; each of R⁴⁵ and R⁴⁶independently represents a hydrogen atom, a halogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms, provided that the plurality of R⁴⁵ to R⁴⁶ may be the same ordifferent from each other; a1 represents an integer of 1 to 5; and R⁷″represents an organic group containing a fluorine atom.

In the formula (f1-1B), R is the same as defined above, and ispreferably a hydrogen atom or a methyl group.

Examples of the halogen atom for R⁴⁵ and R⁴⁶ in the formula (f1-1B)include a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable. Examples of thealkyl group of 1 to 5 carbon atoms for R⁴⁵ and R⁴⁶ include the samealkyl group of 1 to 5 carbon atoms as those defined above for theaforementioned R, and a methyl group or an ethyl group is preferable.Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsfor R⁴⁵ or R⁴⁶ include groups in which part or all of the hydrogen atomsof the aforementioned alkyl groups of 1 to 5 carbon atoms have beensubstituted with halogen atoms. Examples of the halogen atom include afluorine atom, chlorine atom, bromine atom and iodine atom, and afluorine atom is particularly desirable. Among these, R⁴⁵ and R⁴⁶ arepreferably a hydrogen atom, a fluorine atom or an alkyl group of 1 to 5carbon atoms, and more preferably a hydrogen atom, a fluorine atom, amethyl group or an ethyl group.

In formula (f1-1B), a1 represents an integer of 1 to 5, preferably aninteger of 1 to 3, and more preferably 1 or 2.

In formula (f1-1B), R⁷″ represents an organic group containing afluorine atom, and is preferably a hydrocarbon group containing afluorine atom.

The hydrocarbon group containing a fluorine atom may be linear, branchedor cyclic, and preferably has 1 to 20 carbon atoms, more preferably 1 to15 carbon atoms, and particularly preferably 1 to 10 carbon atoms.

The hydrocarbon group having a fluorine atom preferably has 25% or moreof the hydrogen atoms within the hydrocarbon group fluorinated, morepreferably 50% or more, and most preferably 60% or more, as thehydrophobicity of the resist film during immersion exposure is enhanced.

As R⁷″, a fluorinated hydrocarbon group of 1 to 5 carbon atoms isparticularly preferable, and most preferably methyl group, —CH₂—CF₃,—CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CH₂—CF₃ and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography (GPC)) of thecomponent (F1) is not particularly limited, but is preferably 1,000 to80,000, more preferably 5,000 to 60,000, and most preferably 10,000 to50,000. Further, the weight average molecular weight (Mw) of thecomponent (F) is preferably 1,000 to 50,000, more preferably 5,000 to40,000, and most preferably 10,000 to 30,000. When the weight averagemolecular weight is not more than the upper limit of the above range,the component (F) exhibits satisfactory solubility in a resist solventwhen used in a resist composition. On the other hand, when the weightaverage molecular weight is at least as large as the lower limit of theabove range, the dry etching resistance and the cross-sectional shape ofthe resist pattern are improved.

The dispersity (Mw/Mn) of the component (F1) is not particularlylimited, but is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, andmost preferably 1.0 to 2.5. Further, the dispersity (Mw/Mn) of thecomponent (F) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, andmost preferably 1.2 to 2.5. Here, Mn represents the number-averagemolecular weight.

The component (F1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding to thestructural units contained therein, using a radical polymerizationinitiator such as azobisisobutyronitrile (AIBN).

Furthermore, in the component (F1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (F1). This type of copolymer having anintroduced hydroxyalkyl group in which part of the hydrogen atoms of thealkyl group have been substituted with fluorine atoms is effective inreducing developing defects and line edge roughness (LER: unevenness inthe side walls of a line pattern).

Compound (F11)

The component (F11) is a compound (provided that a compound which doesnot contain an acid decomposable group which exhibits increased polarityby the action of acid) represented by general formula (f11-1) shownbelow.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Arepresents —O— or —NH—; X₀ represents a single bond or a divalentlinking group; R₀ represents an organic group; at least one of X₀ and R₀contains a fluorine atom or a silicon atom; and v is 0 or 1.

In general formula (f11-1), R, A, R₀, X₀ and v is the same as R, A, R₀,X₀ and v described above in the aforementioned general formula (f1-1),respectively.

Specific examples of the compound represented by general formula (f11-1)and containing a fluorine atom include monomers providing structuralunits represented by the aforementioned general formulas (f1-11) to(f1-15).

Of these, since the enhanced water repellency effect on the surface of aresist film can be achieved, a monomer providing structural unitsrepresented by formula (f1-13) or (f1-15) is preferable.

Examples thereof include a monomer providing specific examples of thestructural units represented by formulas (f1-11) to (f1-15) describedabove.

Specific examples of the compound represented by general formula (f11-1)and containing a silicon atom include a silicon-containing compoundincluding an organic group containing a trialkylsilyl group or asiloxane bond.

Of these, a monomer providing a silicon-containing structural unit inwhich R₀ in the aforementioned formula (f1-1) is an organic groupcontaining a trialkylsilyl group or a siloxane bond is preferable.

As the component (F), one type of organic compound may be used alone, ortwo or more types of organic compounds may be used in combination.

Among these, since an enhanced water repellency effect on the surface ofa resist film, reduced defects, and excellent shape of the resistpattern can be achieved, it is preferable that the component (F) includethe polymer having a structural unit represented by the aforementionedgeneral formula (f1-1), or the compound represented by general formula(f11-1).

In the resist composition, the amount of the component (F), relative to100 parts by weight of the component (A) is preferably from 0.1 to 20parts by weight, more preferably from 0.5 to 10 parts by weight, andmost preferably from 1 to 5 parts by weight.

When the amount of the component (F) is at least as large as the lowerlimit of the above-mentioned range, the surface of a resist filmexhibits excellent water repellency, and effect of improving propertiesof resist patterns formed in the resolution limit becomes excellent. Onthe other hand, when the amount of the component (F) is no more than theupper limit of the above-mentioned range, shape of the resist patternand lithography properties become excellent.

Amine; Component (D)

In the resist composition of an aspect according to the presentinvention, an amine (D) (hereafter referred to as “component (D)”) maybe added to the resist composition.

When the resist composition contains the component (G) as an acid supplycomponent, in the resist composition liquid, the solubility of thecomponent (A) in the alkali developing solution is likely to beincreased by the action of the component (G). The occurrence of thisphenomenon can be suppressed by controlling the acidity of the component(G) at an appropriate level, and also can be suppressed by adding thecomponent (D) to reduce the acidity of the component (G) in the resistcomposition liquid. When the component (D) is used, it is preferablethat raw materials such as the component (G) can be freely selected.

In addition, during storage of the resist composition, by virtue of thecomponent (D), the storage stability after preparation of the resistcomposition liquid can be enhanced. Furthermore, by removing thecomponent (D) from the resist film before neutralization in the step(3), lithography properties and pattern shape become particularlyexcellent, because the neutralization of base generated from thecomponent (C) with the acid derived from the component (Z) in the step(3) is not suppressed by the component (D).

A multitude of these components (D) have already been proposed, and anyof these known compounds may be used. It is particularly desirable thatthe pKa of the component (D) is equal to or less than the pKa of thecation moiety of the aforementioned component (G1). That is, the pKa ofthe component (D) is preferably 7 or less, and more preferably 6 orless.

When the resist composition contains the component (G1), it is morepreferable that the pKa of the component (D) is less than or equal tothe pKa of the cation moiety of the component (G1) so as to prevent acation of the component (G1) from being exchanged with the component(D).

When the resist composition contains the component (G2), it is desirablethat the basicity of the component (D) is low enough to suppress theextreme acidity deterioration of the component (G2), and the pKa of thecomponent (D) is preferably 7 or less, and more preferably 6 or less.

As the component (D) which satisfies the above pKa, an amine in whichone of “H⁺” bonded to an nitrogen atom (N) has been removed from anamine represented by the formula (G1c-1) described in relation to thecomponent (G1) can be mentioned. Specifically, a compound in which “NH₃⁺” at the terminal of the specific examples of the compounds representedby the formulas (G1c-11) and (G1c-13) has been replaced by “NH₂”; and acompound in which “NH⁺” within the ring in the specific examples of thecompounds represented by the formula (G1c-12) has been replaced by “N”are preferable.

In addition, it is desirable that the component (D) is an amine having arelatively low boiling point. By virtue of the amines having arelatively low boiling point, when coating and forming a resist film inthe step (1), when conducting a baking (PEB) before neutralization inthe step (3), or when conducting a prebake (PAB) which can bearbitrarily conducted after the step (1) and before the exposure in thestep (2), the component (D) can be removed from the resist film. Thecomponent (D) exists while the resist composition is stored, and thecomponent (D) can be removed from the resist film before neutralizationin the step (3). Accordingly, while enhancing the storage stability ofthe resist composition after preparation of the resist compositionliquid, neutralizing the base generated from the component (C) in thestep (3) and the component (G) is never prevented by the component (D).Therefore, particularly excellent lithography properties and shape ofthe resist pattern can be obtained.

As the component (D) which satisfies the above boiling point, an aminehaving a boiling point of 130° C. or lower is preferable, and an aminehaving a boiling point of 100° C. or lower is more preferable, and anamine having a boiling point of 90° C. or lower is particularlypreferable.

Specific examples of the component (D) which satisfies the above pKa andboiling point, aliphatic amine compounds having a fluorinated alkylgroup such as trifluoroethylamine (2,2,2-trifluoroethylamine),pentafluoropropylamine (2,2,3,3,3-pentafluoropropylamine),heptafluorobutylamine (1H,1H-heptafluorobutylamine),nonafluoropentylamine (1H,1H-nonafluoropentylamine),undecafluorohexylamine (1H,1H-undecafluorohexylamine),bis(2,2,2-trifluoroethyl)amine, bis(2,2,3,3,3-pentafluoropropyl)amine,and 1-(2,2,2-trifluoroethyl)pyrrolidine; pyridine-based compound such aspyridine and pentafluoropyridine; and oxazole-based compound such asoxazole and isoxazole.

The resist composition according to the third aspect of the presentinvention includes an amine as the component (D), and the amount of theamine is 1 mol or more, per 1 mol of the component (G).

The resist composition of the present invention includes the component(G) which exhibits acidity by itself as an essential component. Hence, aproblem arises in that if the resist composition is stored afterpreparation thereof, the solubility of the component (A) in the alkalideveloping solution is increased by the action of the component (G)within the resist composition before forming a resist pattern. In theresist composition according to the third aspect of the presentinvention, since one mol or more of the component (D) is used per 1 molof the component (G), it is possible that the acidity of the component(G) is reduced in the resist composition to enhance the storagestability of the resist composition.

A multitude of these components (D) have already been proposed, and anyof these known compounds may be used.

As such an amine, an amine represented by general formula (D-1) shownbelow can be given.

In the formula, R^(101d), R^(101e) and R^(101f) are the same asR^(101d), R^(101e) and R^(101f) in the aforementioned general formula(G1c-1).

In the formula (D-1), the alkyl group for R^(101d) to R^(101f) includesthe same alkyl groups as those described in the aforementioned generalformula (G1c-1). The alkyl group for R^(101d) to R^(101f) preferably has1 to 10 carbon atoms, and more preferably 2 to 6 carbon atoms.

An alkenyl group, an oxoalkyl group, an oxoalkenyl group, an aryl group,an arylalkyl group, an aralkyl group and an aryloxoalkyl group forR^(101d) to R^(101f) is the same as defined above in the aforementionedgeneral formula (G1c-1).

The hydrogen atoms within the alkyl group, the alkenyl group, theoxoalkyl group, the oxoalkenyl group, the aryl group, the arylalkylgroup, the aralkyl group and the aryloxoalkyl group for R^(101d) toR^(101f) may or may not be substituted with a halogen atom such as afluorine atom, an alkoxy group or a sulfur atom.

As an example in the case that R^(101d) to R^(101f) has the substituent,primary, secondary and tertiary amines can be used.

The primary amine or the secondary amine is preferable in terms of theirweak basicity.

Monoalkylamines such as ethylamine (17° C.), propylamine (48° C.),butylamine (78° C.), n-pentylamine (104° C.), n-hexylamine (130° C.) andn-heptylamine (155° C.), or mono(fluorinated)alkylamines in which partof the hydrogen atoms bonded to the second or later position of carbonatoms in the alkyl groups are fluorinated such as trifluoroethylamine(36° C.), pentafluoropropylamine (50° C.), heptafluorobutylamine (70°C.), nonafluoropentylamine (87° C.) and undecafluorohexylamine (107°C.);

dialkylamines such as diethylamine (55° C.), di-n-propylamine (110° C.),di-n-heptylamine (148° C.) and dicyclohexylamine (134° C.), ordi(fluorinated)alkylamines in which part of the hydrogen atoms bonded tothe second or later position of carbon atoms in the alkyl groups isfluorinated such as bis(trifluoroethyl)amine (81° C.) andbis(pentafluoropropyl)amine (103° C.);

primary or secondary (substituted) aromatic amines such as aniline (184°C.), methylphenylamine (195° C.), 2-methoxy-N-methylaniline (115° C.),m-methoxyaniline (80° C.) and methylaniline (199 to 203° C.) are morepreferable.

Further, R^(101d) and R^(101e), or R^(101d), R^(101e) and R^(101f) maybe mutually bonded to form a ring with the nitrogen atom. Examples ofthe formed ring include a pyrrolidine ring, a piperidine ring, ahexamethylene imine ring, an azole ring, a pyridine ring, a pyrimidinering, an azepine ring, a pyrazine ring, a quinoline ring and abenzoquinoline ring.

Further, the ring may contain an oxygen atom in the ring skeletonthereof, and specific examples of preferable rings which contain anoxygen atom include an oxazole ring and an isooxazole ring.

When R^(101d) to R^(101f) form a cyclic amine, specific examplesinclude:

aliphatic monocyclic amines such as piperidine, piperazine, pyrrolidineand 1-(2,2,2-trifluoroethyl)pyrrolidine;

aliphatic polycyclic amines such as 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine and1,4-diazabicyclo[2.2.2] octane;

hetero condensed ring-based cyclic amines such as pyridine,pentafluoropyridine, pyridazine, pyrimidine, pyrazine, oxazole andisooxazole.

The hetero condensed ring-based cyclic amine is preferable, in terms oftheir weak basicity.

Of these, the component (D) is preferably an amine having a relativelylow boiling point, because excellent lithography properties can furtherbe obtained in addition of the effects of the present invention.

By virtue of the amines having a relatively low boiling point, whencoating and forming a resist film in the step (1), when conducting abaking (PEB) before neutralization in the step (3), or when conducting aprebake (PAB) which can be arbitrarily conducted after the step (1) andbefore the exposure in the step (2), the component (D) can be removedfrom the resist film. The component (D) exists while the resistcomposition is stored, and the component (D) can be removed from theresist film before neutralization in the step (3). Accordingly, whileenhancing the storage stability of the resist composition afterpreparation of the resist composition liquid, neutralizing the basegenerated from the component (C) in the step (3) and the component (G)is never prevented by the component (D). Therefore, particularlyexcellent lithography properties and shape of the resist pattern can beobtained.

Specifically, an amine having a boiling point of 130° C. or lower ispreferable, and an amine having a boiling point of 100° C. or lower ismore preferable, and an amine having a boiling point of 90° C. or loweris particularly preferable.

Further, as the component (D) in the third aspect of the presentinvention, an amine having relatively weak basicity is preferable.Specifically, an amine having a pKa of −2 to 7 is preferable, morepreferably a pKa of −1 to 6, and still more preferably a pKa of 0 to 6.

When the pKa of the component (D) is at least as large as the lowerlimit of the above-mentioned range, deterioration of the storagestability caused by the resist liquid being excessively acidic due tothe component (G1) or the component (G2) can be prevented.

On the other hand, when the pKa of the component (D) is no more than theupper limit of the above-mentioned range, the resist compositionexhibits weak basicity. Accordingly, deactivation of an acid at anunexposed portion can be prevented. Further, in the case where thecomponent (G) includes the component (G1), the cation of the component(G1) and the component (D) can be prevented from being exchanged.

Preferable examples thereof include:

(1) an amine in which at least one of R^(101d) to R^(101f) is an alkenylgroup, an oxoalkyl group, an oxoalkenyl group, an aryl group, an aralkylgroup and an aryloxoalkyl group in the aforementioned formula (D-1);

(2) an amine in which at least one of R^(101d) to R^(101f) is an alkylgroup wherein the hydrogen atoms of the alkyl group is substituted witha halogen atom such as a fluorine atom, an alkoxy group or a sulfur atomin the aforementioned formula (D-1);

(3) a cyclic amine in which R^(101d) to R^(101f) form a condensed ringwith the nitrogen atom, or which contains an oxygen atom in the ringskeleton of the condensed ring.

In the case of (1) or (2), a primary or a secondary amine is morepreferable, and still more preferably an amine compound in which ahydrogen atom has been removed from an ammonium cation in theaforementioned formula (G1c-11) or (G1c-11).

Specific examples of particularly preferable component (D) include:

aliphatic amine compounds having a fluorinated alkyl group such astrifluoroethylamine (2,2,2-trifluoroethylamine), pentafluoropropylamine(2,2,3,3,3-pentafluoropropylamine), heptafluorobutylamine(1H,1H-heptafluorobutylamine), nonafluoropentylamine(1H,1H-nonafluoropentylamine), undecafluorohexylamine(1H,1H-undecafluorohexylamine), bis(2,2,2-trifluoroethyl)amine,bis(2,2,3,3,3-pentafluoropropyl)amine, and1-(2,2,2-trifluoroethyl)pyrrolidine;

pyridine-based compounds such as pyridine and pentafluoropyridine; and

oxazole-based compounds such as oxazole and isoxazole.

As the component (D), one type of compound may be used alone, or two ormore types of compounds may be used in combination.

In the resist composition according to the third aspect of the presentinvention, the amount of the component (D) is 1 mol or more, per 1 molof the component (G), preferably 1 to 10 mol per 1 mol of the component(G), more preferably 1 to 8 mol per 1 mol of the component (G), andstill more preferably 1 to 5 per 1 mol of the component (G). When theamount of the component (D) is 1 mol or more, per 1 mol of the component(G), it is possible that acidity is reduced within the resist liquid toenhance the storage stability of the resist composition. On the otherhand, when the amount of the component (D) is 10 mol or less, per 1 molof the component (G), increasing the solubility of the component (A) atunexposed portions in the alkali developing solution by the component(G) excellently proceeds. Therefore, lithography properties becomeparticularly excellent.

When an aspect of the resist composition according to the presentinvention contains the component (D), the amount of the component (D)relative to 100 parts by weight of the component (A) is preferablywithin a range from 0.01 to 20.0 parts by weight, more preferably from 1to 15 parts by weight, and particularly preferably from 2 to 10 parts byweight. Further, in the resist composition according to the third aspectof the present invention, the amount of the component (D) relative to100 parts by weight of the component (A) is preferably within a rangefrom 0.5 to 30 parts by weight, more preferably from 1 to 25 parts byweight, still more preferably from 1.5 to 20 parts by weight, andparticularly preferably from 2 to 15 parts by weight. By ensuring theabove-mentioned range, the storage stability is improved, andlithography properties and resist pattern shape are also improved.

Other Components

The resist composition of the present invention may include a componentother than the component described above, for example, an acid amplifiercomponent or the like.

Acid Amplifier Component; Component (H)

The resist composition of the present invention may further contain anacid amplifier component (H) (hereafter, referred to as “component (H)”)as optional components. In the present invention, the component (H) isdecomposed by an acid to generate a free acid, and the free acid furtherdecomposes the component (H) to further generate free acid. In thismanner, by the action of acid, the component (H) is serially decomposed,and generates many free acid molecules.

The component (H) is not particularly limited, as long as it isdecomposable by the action of an acid, and is capable of furthergenerating acid to self-catalytically amplify acid. Preferable examplesof the component (H) include compounds having a bridged-carbon ringskeleton structure.

Here, the term “compound having a bridged-carbon ring skeletonstructure” refers to a compound which has a structure of a bridging bondformed by a plurality of carbon rings in a molecule thereof.

By virtue of the compound having a bridged-carbon ring skeletonstructure having a bridging bond, the molecule becomes rigid, and thethermal stability of the compound is improved.

The number of carbon rings is preferably from 2 to 6, and morepreferably 2 or 3.

The bridged carbon ring may have part or all of the hydrogen atomssubstituted with an alkyl group, an alkoxy group or the like. The alkylgroup preferably has 1 to 6 carbon atoms, more preferably 1 to 3, andspecific examples of the alkyl group include a methyl group, an ethylgroup and a propyl group. The alkoxy group preferably has 1 to 6 carbonatoms, more preferably 1 to 3, and specific examples of the alkoxy groupinclude a methoxy group and an ethoxy group. The bridged carbon ring mayhave an unsaturated bond such as a double bond.

In the present invention, it is most preferable that the bridged carbonhas, on the ring thereof, a hydroxy group and a sulfonate grouprepresented by general formula (Hs) shown below bonded to the carbonatom adjacent to the carbon atom having the hydroxy group bondedthereto.

[Chemical Formula 96]

—OSO₂—R⁰  (Hs)

In the formula, R⁰ represents an aliphatic group, an aromatic group or aheterocyclic group.

In the aforementioned formula (Hs), R⁰ represents an aliphatic group, anaromatic group or a heterocyclic group.

Examples of the aliphatic group for R⁰ include a chain-like or cyclicalkyl group or an alkenyl group, and preferably has 1 to 12 carbonatoms, more preferably 1 to 10 carbon atoms.

The aromatic group may be either a monocyclic group or a polycyclicgroup, and specific examples thereof include aryl groups.

The heterocyclic group may be a monocyclic group or a polycyclic group,and specific examples thereof include groups which are derived fromvarious conventional heterocyclic compounds.

The aforementioned aliphatic group, aromatic group and heterocyclicgroup may have a substituent, and examples of the substituent include ahalogen atom, an alkyl group, an alkoxy group, an amino group, asubstituted amino group and an oxygen atom (═O).

Specific examples of the aforementioned aliphatic group and the aromaticgroup include a methyl group, an ethyl group, a propyl group, a butylgroup, an acyl group, a hexyl group, a vinyl group, a propylene group,an allyl group, a cyclohexyl group, a cyclooctyl group, abicyclohydrocarbon group, a tricyclohydrocarbon group, a phenyl group, atolyl group, a benzyl group, a phenethyl group, a naphthyl group, anaphthylmethyl group, and substitution products thereof.

Examples of the heterocyclic group include groups derived from variousheterocyclic groups, such as a 5-membered ring compound containing onehetero atom or a condensed ring compound thereof (e.g., furan,thiophene, pyrrole, benzofuran, thionaphthene, indole or carbazole); a5-membered ring compound containing two hetero atoms or a condensed ringcompound thereof (e.g., oxazole, thiazole or pyrazole); a 6-memberedring compound containing one hetero atom or a condensed ring compoundthereof (e.g., pyran, pyrone, coumarin, pyridine, quinoline,isoquinoline or acridine); and a 6-membered ring compound containing twohetero atoms or a condensed ring compound thereof (e.g., pyridazine,pyrimidine, pyrazine or phthalazine).

In the present invention, when the component (H) has, on the bridgedcarbon ring, a hydroxy group and a sulfonate group represented by theaforementioned general formula (Hs), such a component (H) is decomposedby the action of an acid to generate a new acid (R⁰SO₃H).

In this manner, one acid increases in one reaction, and the reaction isaccelerated as the reaction proceeds, thereby serially decomposing thecomponent (H).

In such a case, the strength of the generated acid in terms of the aciddissociation constant (pKa) is preferably 3 or less, and most preferably2 or less. When the pKa is 3 or less, the generated acid itself islikely to induce the self-decomposition. On the other hand, when thegenerated acid has a weaker strength, it becomes difficult to induce theself-decomposition.

Examples of the free acid (R⁰SO₃H) generated by the above reactioninclude methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid,butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid,heptanesulfonic acid, octanesulfonic acid, cyclohexanesulfonic acid,camphorsulfonic acid, trifluoromethanesulfonic acid,2,2,2-trifluoroethanesulfonic acid, benzenesulfonic acid,p-toluenesulfonic acid, p-bromobenzenesulfonic acid,p-nitrobenzenesulfonic acid, 2-thiophenesulfonic acid,1-naphthalenesulfonic acid and 2-naphthalenesulfonic acid.

Specific examples of the component (H)) include compounds represented bygeneral formulae (H1) to (H4) shown below (hereafter, the compoundscorresponding to general formulae are respectively referred to as“compounds (H1) to (H4)”).

In the formulae, R⁵¹ represents a hydrogen atom, an aliphatic group oran aromatic group; and R⁵² represents an aliphatic group, an aromaticgroup or a heterocyclic group.

In the aforementioned general formulae (H1) to (H3), R⁵¹ represents ahydrogen atom, an aliphatic group or an aromatic group. The aliphaticgroup and the aromatic group for R⁵¹ is the same as defined for thealiphatic group and the aromatic group for the aforementioned R⁰. AsR⁵¹, an aliphatic group or an aromatic group is preferable, an aliphaticgroup is more preferable, a lower (1 to 5 carbon atoms) alkyl group isstill more preferable, and a methyl group is most preferable.

In the aforementioned general formulae (H1) to (H4), R⁵² represents analiphatic group, an aromatic group or a heterocyclic group, and is thesame as defined for R⁰. As R⁵², an aliphatic group or an aromatic groupis preferable, and an aliphatic group is more preferable.

With respect to the compounds (H1) to (H4), the compound (H1) has abridge bond on the 1st and 3rd positions of the bicyclo compound, thecompounds (H2) and (H3) has a bridge bond on the 1st and 4th positionsof the bicyclo compound, and the compound (H4) has a bridge bond on the1st and 6th positions of the bicyclo compound (decarine).

Therefore, in the compounds (H1) to (H4), the conformation change of thecyclohexane ring is greatly suppressed, and hence, the ring structureexhibits rigidity.

As the component (H), for example, a compound in which the bridgedcarbon has, on the ring thereof, a hydroxy group and a sulfonate grouprepresented by general formula (Hs) bonded to the carbon atom adjacentto the carbon atom having the hydroxy group bonded thereto (such as thecompounds (H1) to (H4)) can be readily synthesized by recting a diolcompound with a halide of the sulfonic acid. The diol compound has twoisomers, namely, cis-isomer and trans-isomer, but the cis-isomer isthermally stable, and is therefore preferably used. Further, such acompound can be stably stored as long as an acid does not coexist.

Specific examples of preferable component (H) are shown below.

Among these, as the component (H), in terms of effect of the presentinvention (resolution) and excellent lithography properties, thecompounds (H1) and (H2) are preferable, and the compound (H1) isparticularly preferred. More specifically, it is preferable to use atleast one member selected from the group consisting of compoundsrepresented by chemical formulae (H1-1) to (H1-9), and it is mostpreferable to use a compound represented by chemical formula (H1-9).

As the component (H), one type of compound may be used, or two or moretypes of compounds may be used in combination.

When the resist composition of the present invention contains thecomponent (H), the amount of the component (H) relative to 100 parts byweight of the component (A) is preferably 0.1 to 30 parts by weight, andmore preferably 1 to 20 parts by weight. When the amount of thecomponent (H) is at least as large as the lower limit of theabove-mentioned range, the resolution is improved. On the other hand,when the amount of the component (H) is no more than the upper limit ofthe above-mentioned range, the sensitivity is improved.

When the component (H) is used in combination with the component (G),the mixing ratio of the component (H) to the component (G) ((H)/(G)) interms of molar ratio is preferably in the range of 9:1 to 1:9, morepreferably in the range of 9:1 to 5:5, and particularly preferably 9:1to 6:4. When the amount of the component (H) is at least as large as thelower limit of the above-mentioned range, the resolution can beenhanced. On the other hand, when the amount of the component (H) is nomore than the upper limit of the above-mentioned range, the sensitivitybecomes excellent.

In addition, when the component (H) is used in combination with thecomponent (B), the mixing ratio of the component (H) to the component(B) ((H)/(B)) in terms of molar ratio is preferably in the range of 9:1to 1:9, more preferably in the range of 9:1 to 5:5, and particularlypreferably 9:1 to 6:4. When the amount of the component (H) is at leastas large as the lower limit of the above-mentioned range, the resolutioncan be enhanced. On the other hand, when the amount of the component (H)is no more than the upper limit of the above-mentioned range, thesensitivity becomes excellent.

If desired, other miscible additives can also be added to the resistcomposition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, dyes, sensitizers, and base amplifiers.

As the sensitizers, conventional sensitizers can be given. Specificexamples of the conventional sensitizers include benzophenone-typesensitizers, such as benzophenone andp,p′-tetramethyldiaminobenzophenone; carbazole-type sensitizers;acetophen-type sensitizers; naphthalene-type sensitizers; phenol-typesensitizers; anthracene-type sensitizers, such as 9-ethoxyanthracene;biacetyl; eosin; rose bengal; pyrene; phenothiazine; and anthrone. Inthe resist composition, the amount of the sensitizer, relative to 100parts by weight of the component (A) is preferably from 0.5 to 20 partsby weight.

A base amplifier is decomposed by the action of a base in a chainreaction, and is capable of generating a large amount of base using asmall amount of base. Therefore, by blending a base amplifier, thesensitivity of the resist composition can be improved. As the baseamplifier, for example, those described in Japanese Unexamined PatentApplication, First Publication No. 2000-330270 and Japanese UnexaminedPatent Application, First Publication No. 2008-174515 can be used.

Organic Solvent Component; Component (S)

In the present invention, the resist composition can be prepared bydissolving the materials for the resist composition in an organicsolvent (hereafter, referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methylethyl ketone, cyclohexanone, methyl-n-pentyl ketone,methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, cyclohexanone and EL are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2. For example, when EL is mixed as the polar solvent, the PGMEA:ELweight ratio is preferably from 1:9 to 9:1, and more preferably from 2:8to 8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferablyfrom 2:8 to 8:2, and still more preferably 3:7 to 7:3. Alternatively,when PGME and cyclohexanone is mixed as the polar solvent, thePGMEA:(PGME+cyclohexanone) weight ratio is preferably from 1:9 to 9:1,more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of γ-butyrolactone withPGMEA, EL or the aforementioned mixed solvent of PGMEA with a polarsolvent, is also preferable. The mixing ratio (former:latter) of such amixed solvent is preferably from 70:30 to 95:5.

The amount of the component (S) is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 1 to 20% by weight, and preferably from 2 to 15% by weight.

The resist composition according to the first aspect of the presentinvention described above can satisfactorily be used for formation ofthe negative pattern in an alkali developing process and has excellentstorage stability.

The resist composition includes a base component that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component that generates a base upon exposure, anacid supply component and a compound (F) containing at least oneselected from the group consisting of a fluorine atom and a silicon atomand containing no acid decomposable group which exhibits increasedpolarity by the action of acid.

The component (F) is readily segregated at the surface of the resistfilm in formation of a resist film. Therefore, usage of the component(F) can impart water repellency to the resist film formed.

Further, when the component (F) is used, with an object that an exposedportion is immediately dissolved and removed by a developing solutionafter development, a compound (F) into which is introduced an aciddecomposable group is preferably used in an alkali developing process.In intensive studies by the present inventors, if an acid supplycomponent is included in the resist composition containing a compound(F) into which is introduced an acid decomposable group, the solubilityof the component (F) in an alkali developing solution is increased dueto action of the acid supply component during the storage of the resistliquid after preparation of the resist composition. Accordingly, anotherproblem arises in that the resist film is difficult to be imparted waterrepellency. Even though a resist pattern is formed using the resistcomposition deteriorated as described above, patterns having targeteddimensions can not be obtained or no pattern is obtained.

In the first aspect of the present invention, when the resistcomposition including a component (F) containing no acid decomposablegroup is used, the component (F) is not subjected to influence of theacid supply component during the storage of the resist liquid.Accordingly, patterns having targeted dimensions are stably formed, evenafter the resist composition is aged in the storage.

The resist composition of the present invention is suitable for a resistcomposition used in the step (1) of the method of forming a resistpattern including the steps (1) to (4) described later.

In addition, the resist film formed using the resist composition of thepresent invention including the compound (F) exhibit enhanced waterrepellency as compared to a resist film formed using a resistcomposition which does not include the component (F).

Particularly in the immersion exposure process, the resist film is notsubjected to influence of an immersion medium such as water, it ispreferable that the resist film have enhanced hydrophobicity. Further,since the resist film formed using the resist composition of the presentinvention exhibits enhanced hydrophobicity during the immersion exposureas compared with a conventional resist composition, for example, in theimmersion exposure, the resist film exhibits extremely excellent watertracking ability required in the case of conducting immersion exposureusing scanning type of exposure apparatus for the immersion exposure.Therefore, speed-up of the scanning can be achieved.

By virtue of using the component (F) described above, the resist filmformed using the resist composition of the present invention exhibitsenhanced hydrophobicity as compared with the resist film formed using aconventional resist composition. Therefore, the contact angles relativeto water, such as the static contact angle (the contact angle betweenthe surface of a water droplet on the resist film in a horizontal stateand the resist film surface), and the dynamic contact angles (includingthe contact angle at which a water droplet starts to slide when theresist film is inclined, the contact angle at the front-end point of thewater droplet in the sliding direction (the advancing angle), and thecontact angle at the rear-end point of the water droplet in the slidingdirection (the receding angle)), and the sliding angle (the inclinationangle of the resist film at which a water droplet starts to slide whenthe resist film is inclined) are changed. The higher the hydrophobicityof the resist film, the larger the static contact angle and the dynamiccontact angles, and the smaller the sliding angle.

FIG. 1 is a diagram showing an advancing angle (θ₁), a receding angle(θ₂) and a sliding angle (θ₃).

As shown in FIG. 1, the advancing angle is an angle θ₁ between surfaceof a liquid droplet 11 in a lower end 1 a thereof and a plane surface 12where the liquid droplet 11 starts to move (slide) on the plane surface12 when the plane surface 12 on which the liquid droplet 11 is disposedis gradually inclined.

Further, in the case where the liquid droplet 11 starts to move (slide)on the plane surface 12, the receding angle is an angle θ₂ betweensurface of a liquid droplet 11 in a upper end 1 b thereof and the planesurface 12, and the sliding angle is an inclination angle θ₃ of theplane surface 12.

In the present invention, the static contact angle, the dynamic contactangles and the sliding angle indicate, for example, values measuredshown below.

First, a resist composition liquid solution is spin-coated on a siliconsubstrate, subsequently, heated at prescribed condition, for example, attemperature condition of 110 to 115° C. for 60 seconds, thereby forminga resist film.

Next, the angles for the above resist film can be measured usingcommercially available measurement apparatuses such as DROP MASTER-700(product name; manufactured by Kyowa Interface Science Co., Ltd.), AUTOSLIDING ANGLE: SA-30DM (product name; manufactured by Kyowa InterfaceScience Co., Ltd.), and AUTO DISPENSER: AD-31 (product name;manufactured by Kyowa Interface Science Co., Ltd.).

Particularly in the resist composition of the present invention, ameasured value of the receding angle in the resist film obtained usingthe resist composition before exposure or development is preferably 65°or more, more preferably 70° or more, and still more preferably 73° ormore. Preferable value of the upper limit of the receding angle is notparticularly limited, and is, for example, 95° or less.

Values of the angles (the static contact angle, the dynamic contactangles and the sliding angle) in various contact angles described abovecan be controlled by appropriately selecting or adjusting a compositionaccording to the resist composition, for example, the type of thecomponent (F), the amount of the component (F) or the type of thecomponent (A1). For example, the more the amount of the component (F),the resist film formed exhibit more enhanced hydrophobicity. Hence, theresist film has large static contact angle and sliding angle, and thesliding angle thereof is particularly large. Further, when the amount ofthe component (F) or the amount of a fluorine atom within the structuralunits is adjusted, the advancing angle can particularly be controlled(if the amount of a fluorine atom is lower, the resist film has smalleradvancing angle).

In addition, by virtue of using the resist composition of the presentinvention, substance elution from the resist film can be suppressedduring immersion exposure.

That is, the immersion lithography is a method including a step in whichexposure (immersion exposure) is conducted in a state where the regionbetween the lens and the resist film formed on the wafer (which wasconventionally filled with air or an inert gas such as nitrogen) isfilled with a solvent (a immersion medium) that has a larger refractiveindex than the refractive index of air. In immersion exposure, when theresist film is in contact with immersion medium, substances (thecomponent (C), the component (Z) or the like) within the resist film areeluted (substance elution) into immersion medium. The substance elutioncauses the phenomenon such as modification of resist layer and change ofthe refractive index of the immersion medium. Accordingly, lithographyproperties are deteriorated.

The amount of the substance elution is influenced by property (forexample, hydrophilicity, hydrophobicity or the like) of the surface ofthe resist film. Hence, it is presumed that for example, by enhancinghydrophobicity in surface of the resist film, the substance elution isreduced.

When the substance elution is suppressed, modification of resist layerand change of the refractive index of the immersion medium can besuppressed in immersion exposure. Since variation of the refractiveindex of the immersion medium is suppressed, the resist pattern havingexcellent shape or the like can be formed. Further, it is possible toreduce contamination of the lens in the exposure apparatus. Therefore,protective measures therefor are not necessary, and it can contribute tosimplifying the process and the exposure apparatus.

Further, according to the resist composition of the third aspect or thefifth aspect, there are provided a resist composition which can besatisfactorily used for formation of the negative pattern by using aresist composition including a base component that exhibits increasedsolubility in an alkali developing solution under the action of acid inan alkali developing process and which has an excellent storagestability. Although the reasons that this effect is obtained are notentirely clear, they are thought to include the following.

In a method of forming the negative pattern using a base component thatexhibits increased solubility in an alkali developing solution under theaction of acid, that is, a base component known for a conventionalpositive resist composition in an alkali developing process, it isnecessary that an acidic compound component provided to the resist filmin advance and a base generated at an exposed portion upon the exposureare neutralized.

In the case, if a compound that exhibits acidity by itself is used as anacidic compound component (G) instead of an acid generator (B) whichgenerates an acid by heating or upon exposure, material which isgenerated by the action of exposure or heating is only the base.Therefore, the process is simplified. In addition, neutralizationefficiency is independent from acid generation efficiency. Accordingly,neutralization reaction and formation of pattern is satisfactorilyperformed.

On the other hand, when the component (G) that exhibits acidity byitself and has proton donating ability is used, another problem arisesin that the solubility of the component (A) in an alkali developingsolution is increased due to the component (G) having acidity during thestorage of the resist liquid after preparation of the resist compositionincluding the component (A) and the component (G) before forming aresist pattern.

In the resist composition according to the third aspect of the presentinvention, after the novel process is optimized by using a compound thatexhibits acidity by itself and has proton donating ability as thecomponent (G), one mol or more of the component (D) is used per 1 mol ofthe component (G) in addition of the component (G). It is presumed thatin this manner, the acidity is appropriately controlled in the resistliquid, and both of the storage stability and the resolution can beachieved.

Further, in the resist composition according to the fifth aspect of thepresent invention, after the novel process is optimized by using acompound that exhibits acidity by itself and has proton donating abilityas the acidic compound component, a salt containing a cation having thespecific pKa value is used as the acidic compound component. It ispresumed that in this manner, the acidity of the acidic compoundcomponent is appropriately controlled, and both of the storage stabilityand the resolution can be achieved.

Furthermore, when the component (F) is included, or when the component(F) includes the structural unit (f1), the problem often arisessimilarly to the component (A) described above due to action of thecomponent (G). Even in this case, the present invention can achieve bothof the storage stability and the resolution, and is particularly usefulin formation of patterns using immersion exposure. Moreover, when thecomponent (F) includes the structural unit (f1), by further includingthe amine having relatively weak basicity, the storage stability canfurther be improved.

<<Method of Forming Resist Pattern>>

The method of forming a resist pattern of the second aspect of thepresent invention includes the step (1) in which a resist film is formedby coating a resist composition which includes a base component thatexhibits increased solubility in an alkali developing solution under theaction of acid, a photo-base generator component that generates a baseupon exposure, an acid supply component and a compound (F) containing atleast one selected from the group consisting of a fluorine atom and asilicon atom and containing no acid decomposable group which exhibitsincreased polarity by the action of acid, on a substrate; a step (2) inwhich the resist film is subjected to exposure; a step (3) in whichbaking is conducted after the step (2), such that, at an exposed portionof the resist film, the base generated from the photo-base generatorcomponent upon the exposure and an acid derived from the acid supplycomponent are neutralized, and at an unexposed portion of the resistfilm, the solubility of the base component in an alkali developingsolution is increased by the action of the acid derived from the acidsupply component; and a step (4) in which the resist film is subjectedto an alkali development, thereby forming a negative-tone resist patternin which the unexposed portion of the resist film has been dissolved andremoved.

As a resist composition used in the step (1) of the method of forming aresist pattern of the second aspect of the present invention, the sameas those described above in the resist composition of the first aspectof the present invention can be used.

The method of forming a resist pattern of the fourth aspect of thepresent invention includes a step (1) in which a resist film is formedby coating a resist composition which includes a base component (A) thatexhibits increased solubility in an alkali developing solution under theaction of acid, a photo-base generator component (C) that generates abase upon exposure, an acidic compound component (G) and an amine (D),the amount of which is 1 mol or more, per 1 mol of the acidic compoundcomponent (G), on a substrate; a step (2) in which the resist film issubjected to exposure; a step (3) in which baking is conducted after thestep (2), such that, at an exposed portion of the resist film, the basegenerated from the photo-base generator component (C) upon the exposureand the acidic compound component (G) are neutralized, and at anunexposed portion of the resist film, the solubility of the basecomponent (A) in an alkali developing solution is increased by theaction of the acidic compound component (G); and a step (4) in which theresist film is subjected to an alkali development, thereby forming anegative-tone resist pattern in which the unexposed portion of theresist film has been dissolved and removed. That is, in the method offorming a resist pattern of the fourth aspect of the present invention,the resist composition of the third aspect of the present inventiondescribed above in the step (1) is used.

The method of forming a resist pattern of the sixth aspect of thepresent invention includes a step (1) in which a resist film is formedby coating a resist composition which includes a base component (A) thatexhibits increased solubility in an alkali developing solution under theaction of acid, a photo-base generator component (C) that generates abase upon exposure, and an acidic compound component (G) including acompound (G1C) composed of a nitrogen-containing cation having a pKavalue of 7 or less and a counteranion, on a substrate; a step (2) inwhich the resist film is subjected to exposure; a step (3) in whichbaking is conducted after the step (2), such that, at an exposed portionof the resist film, the base generated from the photo-base generatorcomponent (C) upon the exposure and the acidic compound component (G)are neutralized, and at an unexposed portion of the resist film, thesolubility of the base component (A) in an alkali developing solution isincreased by the action of the acidic compound component (G); and a step(4) in which the resist film is subjected to an alkali development,thereby forming a negative-tone resist pattern in which the unexposedportion of the resist film has been dissolved and removed. That is, inthe method of forming a resist pattern of the sixth aspect of thepresent invention, the resist composition of the fifth aspect of thepresent invention described above in the step (1) is used.

In the present invention, the term “prebake” refers to a heatingtreatment of 70° C. or more by a hotplate and the like which isconducted between coating a resist composition on a substrate andexposing it.

A “negative-tone resist pattern” refers to a resist pattern in which anunexposed portion of the resist film is dissolved and removed by analkali developing solution, and an exposed portion remains as a pattern.

Hereinbelow, the method of forming a resist pattern according to thepresent invention will be described, with reference to the drawings.However, the present invention is not limited to these embodiments.

FIG. 2A to FIG. 2D show an example of the second, the fourth and thesixth embodiments of the method of forming a resist pattern according tothe present invention. The second, the fourth and the sixth embodimentsare collectively referred to as “present embodiment”.

In the second embodiment, a resist composition including a basecomponent (component (A)) that exhibits increased solubility in analkali developing solution under the action of acid, a photo-basegenerator component (component (C)) that generates a base upon exposure,an acidic compound (component (G)) as an acid supply (component (Z)) anda compound (F) containing at least one selected from the groupconsisting of a fluorine atom and a silicon atom, and containing no aciddecomposable group which exhibits increased polarity by the action ofacid is used.

Further, in the fourth embodiment, a resist composition including a basecomponent (A) that exhibits increased solubility in an alkali developingsolution under the action of acid, a photo-base generator component (C)that generates a base upon exposure, an acidic compound component (G)and an amine (D) is used.

Furthermore, in the sixth embodiment, a resist composition including abase component (A) that exhibits increased solubility in an alkalideveloping solution under the action of acid, a photo-base generatorcomponent (C) that generates a base upon exposure, and an acidiccompound component (G) is used.

Firstly, as shown in FIG. 2A, the resist composition is applied to asubstrate 1 to form a resist film 2 (step (1); FIG. 2A).

Next, as shown in FIG. 2B, the resist film 2 formed above is subjectedto exposure through a photomask 3 having a predetermined pattern formedthereon. As a result, in the exposed region (exposed portions) of theresist film 2, a base is generated from the photo-base generatorcomponent upon exposure (step (2); FIG. 2B).

After exposure, baking (post exposure bake (PEB)) is conducted. By thisbaking, at the unexposed portions 2 b of the resist film 2, thesolubility of the base component in an alkali developing solution can beincreased by the action of the acid (acidic compound) provided to theresist film 2 by adding the acidic compound to the resist composition.On the other hand, at exposed portions 2 a, a neutralization reactionbetween the base generated from the photo-base generator component uponexposure and the acid provided to the resist film 2 proceeds, so thatthe solubility of the base component in an alkali developing is eitherunchanged or only slightly changed. As a result, a difference in thedissolution rate in an alkali developing solution (dissolution contrast)occurs between the exposed portions 2 a and the unexposed portions 2 b(step (3); FIG. 2C).

Thereafter, developing is conducted using an alkali developing solution.By conducting development, the exposed portions 2 a of the resist film 2remain, and the unexposed portions 2 b of the resist film 2 aredissolved and removed. As a result, as shown in FIG. 2D, a resistpattern including a plurality of resist patterns 2 a arranged atintervals is formed on the substrate 1 (step (4); FIG. 2D).

[Step (1)]

In the second embodiment, a resist composition including a basecomponent that exhibits increased solubility in an alkali developingsolution under the action of acid, a photo-base generator component thatgenerates a base upon exposure, an acidic compound as an acid supplycomponent and a compound (F) containing at least one selected from thegroup consisting of a fluorine atom and a silicon atom, and containingno acid decomposable group which exhibits increased polarity by theaction of acid is applied to a substrate 1 to form a resist film 2.

In the fourth embodiment, a resist composition including a basecomponent (A) that exhibits increased solubility in an alkali developingsolution under the action of acid, a photo-base generator component (C)that generates a base upon exposure, an acidic compound component (G)containing the component (G1) and an amine (D) is applied to a substrate1 to form a resist film 2.

In the sixth embodiment, a resist composition including a base component(A) that exhibits increased solubility in an alkali developing solutionunder the action of acid, a photo-base generator component (C) thatgenerates a base upon exposure, and an acidic compound component (G)containing the component (G1C) is applied to a substrate 1 to form aresist film 2.

The substrate 1 is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate 1, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. The substrates provided with the organic film on thesurface thereof are preferable. As the inorganic film, an inorganicantireflection film (inorganic BARC) can be used. As the organic film,an organic antireflection film (organic BARC) and an organic film suchas a lower-layer organic film used in a multilayer resist method can beused. When the organic film is particularly provided, a pattern canreadily be formed on the substrate with a high aspect ratio.Accordingly, the organic film is useful in the production ofsemiconductors.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer film) and at least one layer of a resistfilm are provided on a substrate, and a resist pattern formed on theupper resist film is used as a mask to conduct patterning of thelower-layer film. This method is considered as being capable of forminga pattern with a high aspect ratio. The multilayer resist method isbroadly classified into a method in which a double-layer structureconsisting of an upper-layer resist film and a lower-layer film isformed, and a method in which a multilayer structure having at leastthree layers composed of an upper-layer resist film, a lower-layer filmand at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer film.In the multilayer resist method, a desired thickness can be ensured bythe lower-layer film, and as a result, the thickness of the resist filmcan be reduced, and an extremely fine pattern with a high aspect ratiocan be formed.

An inorganic film can be formed, for example, by coating an inorganicanti-reflection film composition such as a silicon-based material on asubstrate, followed by baking.

An organic film can be formed, for example, by dissolving a resincomponent and the like for forming the film in an organic solvent toobtain an organic film-forming material, coating the organicfilm-forming material on a substrate using a spinner or the like, andbaking under heating conditions preferably in the range of 200 to 300°C. for 30 to 300 seconds, more preferably for 60 to 180 seconds. Theorganic film-forming material does not need to have susceptibility tolight or electron beam like a resist film, and the organic film-formingmaterial may or may not have such susceptibility. More specifically, aresist or a resin generally used in the production of a semiconductordevice or a liquid crystal display device can be used.

Further, it is preferable that the organic film-forming material can besubjected to etching, particularly dry etching, so that, by etching theorganic film using a resist pattern, the resist pattern can betransferred to the organic film, and an organic film pattern can beformed. It is particularly desirable to use an organic film-formingmaterial which can be subjected to oxygen plasma etching or the like. Assuch an organic film-forming material, a material conventionally usedfor forming an organic film such as an organic BARC can be used.Examples of such an organic film-forming material include the ARC seriesmanufactured by Brewer Science Ltd., the AR series manufactured by Rohmand Haas Company, and the SWK series manufactured by Tokyo Ohka KogyoCo., Ltd.

In the first embodiment, a resist composition includes a base componentthat exhibits increased solubility in an alkali developing solutionunder the action of acid, a photo-base generator component thatgenerates a base upon exposure, an acidic compound as an acid supplycomponent and a compound (F) containing at least one selected from thegroup consisting of a fluorine atom and a silicon atom, and containingno acid decomposable group which exhibits increased polarity by theaction of acid.

The acidic compound acts as an acid by baking (PEB) in the step (3)described later. The acid (acidic compound) causes neutralization withthe base generated from the photo-base generator component upon exposureat exposed portions 2 a of the resist film 2. The acid (acidic compound)acts on the base component at unexposed portions 2 b of the resist film2, thereby increasing the solubility of the base component in an alkalideveloping solution.

For details, the resist composition is the same as the resistcomposition according to the first aspect of the present inventiondescribed above.

Further, the resist composition used in the step (1) according to thefourth aspect of the present invention is the resist composition of thethird aspect described above.

Furthermore, the resist composition used in the step (1) according tothe sixth aspect of the present invention is the resist composition ofthe fifth aspect described above.

The method of applying the resist composition to the substrate 1 to forma resist film 2 is not particularly limited, and the resist film 2 canbe formed by a conventional method.

For example, the resist composition can be applied to the substrate 1 bya conventional method such as spincoat method using a spin coater orbarcoat method using a barcoater, followed by drying on a cooling plateat room temperature or conducting prebake (PAB), thereby forming aresist film 2.

When a prebake treatment is conducted, the temperature condition ispreferably from 80 to 150° C., and the bake treatment time is preferablyfrom 40 to 120 seconds, more preferably from 60 to 90 seconds. Whenconducting prebake, even if the thickness of the resist film is thick,the organic solvent is easily vaporized.

By drying the resist composition at a room temperature and notconducting prebake, it is possible to reduce the number of steps forforming a resist pattern and to enhance the resolution of obtainedresist pattern.

The presence or absence of the prebake can be appropriately determinedin view of the aforementioned advantages, depending on the raw materialsof the resist composition to be used, or depending on the target of thepattern to be formed.

The thickness of the resist film 2 formed in the step (1) is preferably50 to 500 nm, and more preferably 50 to 450 nm. By ensuring that thethickness of the resist film satisfies the above-mentioned range, aresist pattern with a high level of resolution can be formed, and asatisfactory level of etching resistance can be achieved.

In addition, when not conducting prebake, the thickness of the resistfilm 2 formed in the step (1) is preferably 300 nm or less, morepreferably 200 nm or less, and particularly preferably 50 to 150 nm.When the thickness of the resist film 2 is no more than the upper limitof the above-mentioned range, even if prebake is not conducted, anorganic solvent is less likely to be remained and likely to be vaporizedby an application such as spin-coating at a room temperature, and hence,in-plane uniformity of the resist film 2 on the substrate 1 is enhanced.The effect obtained by not conducting prebake can be prominentlyobtained especially in the case of thin resist film.

[Step (2)]

In the present embodiment, the resist film 2 formed in the step (1) isselectively exposed through a photomask 3. As a result, at exposedportions 2 a, a base is generated from the photo-base generatorcomponent upon exposure.

With respect to the exposure dose, an amount capable of generating abase from the photo-base generator component in an amount necessary toneutralize the acid present in the exposed portions 2 a is sufficient.

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as KrF excimer laser,ArF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. In terms of forming a fine resist pattern, ArF excimer laser,EUV or EB is preferable, and ArF excimer laser is particularlydesirable.

The photomask 3 is not particularly limited, and a conventional mask canbe used. For example, a binary mask in which the transmittance of thelight shielding portion is 0% or a halftone-phase shift mask (HT-mask)in which the transmittance of the light shielding portion is 6% can beused. The unexposed portions can be selectively formed by using ahalftone-phase shift mask.

As a binary mask, those in which a chromium film, a chromium oxide film,or the like is formed as a light shielding portion on a quartz glasssubstrate are generally used.

A phase shift mask is a photomask provided with a portion (shifter)which changes the phase of light. Thus, by using a phase shift mask,incidence of light to unexposed portions can be suppressed, and thedissolution contrast to an alkali developing solution can be improvedbetween unexposed portions and exposed portions. As a phase shift maskother than a halftone-phase shift mask, a Levenson-phase shift mask canbe mentioned. As any of these phase shift masks, commercially availablemasks can be used.

Specific examples of the half-tone type phase shift masks include thosein which an MoSi (molybdenum silicide) film, a chromium film, a chromiumoxide film, an silicon oxynitride film, or the like is formed as a lightshielding portion (shifter) exhibiting a transmittance of about several10% (generally 6%) on a substrate generally made of quartz glass.

In the present embodiment, exposure is conducted through a photomask 3,but the present invention is not limited to this embodiment. Forexample, the exposure may be conducted without using a mask, e.g.,selective exposure by drawing with electron beam (EB) or the like.

Further, when the resist composition according to the third aspect orthe fifth aspect of the present invention includes a photo-acidgenerator as the component (B) in addition of the component (G), an acidis generated from the photo-acid generator in the step (2).Specifically, a base from the photo-base generator component and theacid from the photo-acid generator are generated at exposed portions 2 aupon exposure in the step (2). By baking in a step (3) described later,at the unexposed portions 2 b, a protecting group in the base componentis dissociated (deprotection reaction proceeds) under the action of theacid generated at the exposed portions 2 a and diffused to the unexposedportions 2 b, thereby increasing the solubility of the base component inan alkali developing solution. On the other hand, at exposed portions 2a, a neutralization reaction proceeds between the base generated in thestep (2) and the acid. As a result, the solubility of the base componentin an alkali developing is either unchanged or only slightly changed. Assuch, a difference in the dissolution rate in an alkali developingsolution (dissolution contrast) occurs between the exposed portions 2 aand the unexposed portions 2 b.

The exposure of the resist film 2 can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography) through an immersion medium.In step (2), in terms of forming a resist pattern with a highresolution, it is preferable to conduct immersion exposure through animmersion medium.

In immersion lithography, exposure (immersion exposure) is conducted ina state where the region between the lens and the resist film 2 formedon the substrate 1 (which was conventionally filled with air or an inertgas such as nitrogen) is filled with a solvent (a immersion medium) thathas a larger refractive index than the refractive index of air.

More specifically, in immersion lithography, the region between theresist film 2 formed in the above-described manner and lens at thelowermost portion of the exposure apparatus is filled with a solvent (animmersion medium) that has a larger refractive index than the refractiveindex of air, and in this state, the resist film 2 is subjected toexposure (immersion exposure) through a predetermined photomask 3.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film 2 to be subjected to immersion exposure. The refractiveindex of the immersion medium is not particularly limited as long at itsatisfies the above-mentioned requirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film 2 include water, fluorine-basedinert liquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the immersion medium afterthe exposure can be removed by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

[Step (3)]

In the present embodiment, after the step (2), baking (post exposurebake (PEB)) is conducted.

In the baking, the temperature conditions is preferably from 50 to 200°C., more preferably from 80 to 150° C., and still more preferably from90 to 130° C. The baking time is preferably from 10 to 300 seconds, morepreferably from 40 to 120 seconds, and still more preferably from 60 to90 seconds.

In this manner, by conducting baking of the resist film 2 afterexposure, in the entire resist film 2, the acidic compound blended inthe resist composition acts as an acid. The solubility of the basecomponent in an alkali developing solution can be increased by theaction of the acid (acidic compound) at the unexposed portions 2 b ofthe resist film 2. On the other hand, at exposed portions 2 a of theresist film 2, a neutralization reaction between the base generated fromthe photo-base generator component upon exposure and the acid (acidiccompound) proceeds, so that the amount of acid which would act on thebase component decreases. As a result, the solubility of the basecomponent in an alkali developing is either unchanged or only slightlychanged. As such, a difference in the dissolution rate in an alkalideveloping solution (dissolution contrast) occurs between the exposedportions 2 a and the unexposed portions 2 b.

In addition, when the resist composition according to the third aspector the fifth aspect of the present invention includes a thermal-acidgenerator as the component (B) in addition of the component (G), an acidis generated from the thermal-acid generator in the baking step.

The baking in this step (3) does not necessarily control the start ofthe neutralization reaction.

[Step (4)]

In the present embodiment, after the step (3), by conducting alkalideveloping, the unexposed portions 2 b of the resist film 2 aredissolved and removed, and the exposed portions 2 a are retained,thereby forming a negative resist pattern.

Specific examples of the alkali developing solution include inorganicalkalis, such as sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium silicate, sodium metasilicate and aqueous ammonia;primary amines, such as ethylamine and n-propylamine; secondary amines,such as diethylamine and di-n-butylamine; tertiary amines, such astriethylamine and methyldiethylamine; alcoholamines, such asdimethylethanolamine and triethanolamine; quaternary ammonium salts,such as tetramethylammonium hydroxide and tetraethylammonium hydroxide;and cyclic amines, such as pyrrole and piperidine.

Among these examples, as the alkali developing solution, an aqueousalkali solution containing at least one member selected from the groupconsisting of primary amines, secondary amines, tertiary amines andquaternary ammonium salts is preferable, and an aqueous solution oftetramethylammonium hydroxide (TMAH) is particularly desirable.

Further, the aforementioned aqueous alkali solution having alcohols,surfactants added thereto in an appropriate amount may be used.

In general, the alkali concentration within the alkali developingsolution (i.e., concentration of inorganic alkalis, quaternary ammoniumsalts or amine compounds, based on the total weight of the alkalideveloping solution) is from 0.01 to 20% by weight.

The alkali developing treatment can be performed by a conventionalmethod.

After the alkali development, a rinse treatment using pure water or thelike may be conducted.

In addition, after the alkali development, a further baking (post bake)may be conducted. Post bake (which is performed in order to remove watercontent after the alkali developing and rinsing) is generally conductedat about 100° C. preferably for 30 to 90 seconds.

In the present embodiment described above, a resist compositioncontaining an acidic compound as an acid supply component is used, and aresist composition containing an acid generator component (thermal-acidgenerator or photo-acid generator) instead of the acidic compound ortogether with the acidic compound may be used. In addition, an acidamplifier component (H) may be used together with at least one of theacidic compound and the acid generator component, since theconcentration of acid when conducting a baking treatment such as PEB isenhanced.

As the acid generator component, either or both a component whichgenerates an acid by heating (thermal-acid generator) and a componentwhich generates an acid upon exposure (photo-acid generator) can beused.

In the case where a resist composition including the thermal-acidgenerator as the acid generator component is used, an acid is generatedfrom the thermal-acid generator in the entire resist film 2 by baking(PEB) in the step (3). At unexposed portions 2 b in the resist film 2,the solubility of the base component in an alkali developing solutioncan be increased by the action of acid generated from the thermal-acidgenerator by baking (PEB). On the other hand, at exposed portions 2 a inthe resist film 2 a, a neutralization reaction between the acidgenerated from the thermal-acid generator by baking (PEB) and the basegenerated from the photo-base generator component upon exposure in theaforementioned step (2) proceeds, and the solubility of the basecomponent in an alkali developing solution is either unchanged or onlyslightly changed. As such, a difference in the dissolution rate in analkali developing solution (dissolution contrast) occurs between theexposed portions 2 a and the unexposed portions 2 b.

When a resist composition containing a thermal-acid generator is used,it is preferable that the aforementioned prebake be not performed. Bynot conducting a prebake treatment, an acid derived from thethermal-acid generator does not act on the base component after applyingthe resist composition on a substrate and before conducting exposure. Asa result, the contrast between exposed portions 2 a and unexposedportions 2 b in the resist film 2 is increased, and hence, a negativepattern having a high resolution is easily formed.

In addition, when the type of photomask, base component, photo-basegenerator component and the like are appropriately selected, aphoto-acid generator can be used as the acid generator component. Forexample, an embodiment in which a resist composition containing aphoto-acid generator having a relatively long diffusion length and aphoto-base generator having a relatively short diffusion length is used,and a photomask having a transparency (halftone-phase shift mask) isused as a photomask can be mentioned. The diffusion length of the acidcan be adjusted by controlling the skeleton or polarity of an anionmoiety of a photo-acid generator, whereas the diffusion length of basecan be adjusted by controlling the molecular weight or skeleton of thebase generated from the photo-base generator component after aphotodegradation.

In the embodiment, at exposed portions 2 a, a base is generated from thephoto-base generator component and an acid is generated from aphoto-acid generator upon exposure in the step (2). At the unexposedportions 2 b, the protecting group within the base component isdissociated (deprotection reaction proceeds) by the action of acid whichis generated at the exposed portions 2 a and diffused to the unexposedportions 2 b by baking in the step (3), thereby increasing thesolubility of the base component in an alkali developing solution. Onthe other hand, at exposed portions 2 a, a neutralization reactionbetween the base and the acid generated in the step (2) proceeds, andthe solubility of the base component in an alkali developing solution iseither unchanged or only slightly changed. As such, a difference in thedissolution rate in an alkali developing solution (dissolution contrast)occurs between the exposed portions 2 a and the unexposed portions 2 b.

In addition, the method of forming a resist pattern according to thepresent invention may include a step (5) in which a composition forformation of an organic film including an acid supply component isapplied to the resist film to form an organic film between the step (2)and the step (3). After exposure, applying the composition for formationof an organic film to the resist film, subsequently baking (PEB) isconducted. As a result, the organic film is formed on the resist film,and an acid derived from the acid supply component contained in theorganic film is diffused from the organic film to the resist film toprovide an additional acid to the resist film. Thereafter, developing isconducted using an alkali developing solution, thereby forming anegative pattern having a high resolution.

Further, alternatively to use the composition for formation of anorganic film, an embodiment in which an acidic active rinse is onlyapplied to the resist film may be used. As the acidic active rinse, theaforementioned aqueous solution containing the component (G2) can beused.

As examples of the composition for formation of an organic film, inaddition of the acid supply component, a composition including a resin,an organic solvent or the like can be given. The resin is notparticularly limited, and it is preferable to use an alkali-solubleresin because in step (4), the formed organic film can be removed duringthe formation of a resist pattern by alkali developing. As thealkali-soluble resin, any resin having an alkali-soluble group may beused, and examples thereof include conventional resins such as novolakresins, hydroxystyrene resins, acrylic resins and polycycloolefinresins. As the organic solvent, the same as the organic solvent blendedin the resist composition described above such as an alcohol organicsolvent, a fluorine organic solvent or an ether organic solvent havingno hydroxyl group can be used. As the acid supply component, the same asthe acid supply component blended in the resist composition describedabove can be given. When a photo-acid generator is used as the acidsupply component, the step (5) may be conducted between the step (1) andthe step (2).

In the method of forming a resist pattern according to the presentinvention, after forming a negative resist pattern in the manner asdescribed above, etching of the substrate 1 may be conducted using thenegative resist pattern as a mask. By conducting such etching totransfer the resist pattern to the substrate 1, a semiconductor deviceor the like can be produced.

The etching can be conducted by a conventional method. For example, whenthe substrate 1 has an organic film formed thereon, the etching of theorganic film is preferably conducted by dry etching. Among dry etching,especially in terms of production efficiency, oxygen-plasma etching oretching using a CF₄ gas or a CHF₃ gas is preferable, and oxygen-plasmaetching is particularly desirable.

Etching of the substrate is preferably performed using a halogen gas,more preferably using a fluorinated carbon-based gas, and mostpreferably using a CF₄ gas or a CHF₃ gas.

According to the method of forming a resist pattern of the secondaspect, the fourth aspect and the sixth aspect of the present invention,by use of the developing process combined with an alkali developingsolution and a chemically amplified resist composition which had beenused as a positive resist composition, a negative resist pattern havinga high resolution can be formed.

Further, in the method of forming a resist pattern of the second aspectof the present invention, when the resist composition according to thepresent invention described above is used in the step (1), a resistpattern improving both of the storage stability and the resolution canbe formed. That is, according to the method of forming a resist pattern,fine patterns can be formed with excellent precision without influenceof aging.

Furthermore, by the method of forming a resist pattern according to thepresent invention, the resolution becomes excellent in a resist pattern(such as an isolated trench pattern, an extremely small, dense contacthole pattern, or the like) having a region where the optical strengthbecomes weak (region where irradiation by exposure is not satisfactorilyreached) is likely to be generated.

Moreover, by the method of forming a resist pattern according to thepresent invention, it is possible to form a highly densed resistpattern. For example, it becomes possible to form a contact hole patternhaving an excellent shape, in which each of the holes are close to eachother, e.g., the distance between the holes is about 30 to 50 nm.

In addition, the method of forming a resist pattern according to thepresent invention can be performed by existing exposure apparatuses andexisting equipments.

By using a double exposure method in the method of forming a resistpattern according to the present invention, the number of steps can bereduced as compared to a double patterning in which each of alithography step and a patterning step are performed at least twice.

Further, in the method of forming a resist pattern of the fourth aspectof the present invention, when the resist composition according to thethird aspect of the present invention is used in the step (1), theeffects according to the third aspect described above can be obtained,that is, a resist pattern improving both of the storage stability andthe resolution can be formed.

In the method of forming a resist pattern of the sixth aspect of thepresent invention, when the resist composition according to the fifthaspect of the present invention is used in the step (1), the effectsaccording to the fifth aspect described above can be obtained, that is,a resist pattern improving both of the storage stability and theresolution can be formed.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

<Preparation of Resist Compositions>

Examples A1 to A12, Comparative Examples A1 to A3

The components shown in Table 1 were mixed together and dissolved toobtain a resist composition.

TABLE 1 Compo- Compo- Compo- Compo- Compo- Resist nent nent nent nentnent composition (A) (C) (Z) (F) (S) Example (A)-1A (C)-1A (G)-1A (F)-1A(S)-1 A1 [100] [10.0] [8.0] [3.0] [3500] Example (A)-1A (C)-1A (G)-1A(F)-2A (S)-1 A2 [100] [10.0] [8.0] [2.0] [3500] Comparative (A)-1A(C)-1A (G)-1A (F)-3A (S)-1 Example A1 [100] [10.0] [8.0] [3.0] [3500]Comparative (A)-1A (C)-1A (G)-1A (F)-4A (S)-1 Example A2 [100] [10.0][8.0] [2.0] [3500] Example (A)-1A (C)-1A (G)-1A (F)-5A (S)-1 A3 [100][10.0] [8.0] [3.0] [3500] Example (A)-1A (C)-1A (G)-1A (F)-6A (S)-1 A4[100] [10.0] [8.0] [2.0] [3500] Example (A)-1A (C)-1A (G)-1A (F)-7A(S)-1 A5 [100] [10.0] [8.0] [2.0] [3500] Example (A)-1A (C)-1A (G)-1A(F)-8A (S)-1 A6 [100] [10.0] [8.0] [3.0] [3500] Example (A)-1A (C)-1A(G)-1A (F)-9A (S)-1 A7 [100] [10.0] [8.0] [3.0] [3500] Example (A)-1A(C)-1A (G)-1A (F)-10A (S)-1 A8 [100] [10.0] [8.0] [3.0] [3500] Example(A)-1A (C)-1A (G)-1A (F)-11A (S)-1 A9 [100] [10.0] [8.0] [2.0] [3500]Example (A)-1A (C)-1A (G)-1A (F)-12A (S)-1 A10 [100] [10.0] [8.0] [2.0][3500] Example (A)-1A (C)-1A (G)-1A (F)-13A (S)-1 A11 [100] [10.0] [8.0][3.0] [3500] Example (A)-1A (C)-1A (G)-1A (F)-14A (S)-1 A12 [100] [10.0][8.0] [2.0] [3500] Comparative (A)-1A (C)-1A (G)-1A (F)-15A (S)-1Example A3 [100] [10.0] [8.0] [2.0] [3500]

In Table 1, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added, and the reference charactersindicate the following.

(A)-1A: a copolymer represented by chemical formula (A1-1) shown below.Mw: 7,000, Mw/Mn: 1.56. In the chemical formula, the subscript numeralsshown on the bottom right of the parentheses ( ) indicate the percentage(mol %) of the respective structural units.

(C)-1A: a compound represented by chemical formula (C)-1A shown below.

(G)-1A: a compound represented by chemical formula (G)-1A shown below.

(F)-1A to (F)-15A: polymers represented by chemical formulas (F)-1A to(F)-15A, respectively. In the chemical formula, the subscript numeralsshown on the bottom right of the parentheses ( ) indicate the percentage(mol %) of the respective structural units. The weight average molecularweight (Mw) and the dispersity (Mw/Mn) in each of the polymers wereshown in Table 2.

(S)-1: a mixed solvent of propylene glycol monomethyl etheracetate/propylene glycol monomethyl ether (PGMEA/PGME)=6/4 (weightratio).

<Formation of Resist Pattern>

Step (1)

An organic antireflection film composition (product name: ARC29,manufactured by Brewer Science Ltd.) was applied to an 8-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicantireflection film having a thickness of 90 nm.

Next, each of the resist compositions was spin-coated on the organicantireflection film, thereby forming a resist film having a thickness of100 nm.

Step (2)

The resist films formed above were not subjected to a prebake (PAB).Then, the resist films were placed on a cooling plate at 23° C. for 60seconds. The resist film was irradiated with an ArF excimer laser (193nm) through a photomask (6% halftone) targeting a LS pattern with a linewidth of 65 nm (a pitch of 130 nm), using an ArF exposure apparatusNSR-S308 (manufactured by Nikon Corporation; NA (numericalaperture)=0.92; dipole).

Step (3)

Then, a bake treatment (post exposure bake; PEB) was conducted at 95° C.for 60 seconds.

Step (4)

Thereafter, alkali developing was conducted for 30 seconds at 23° C. ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.).

[Evaluation of Resolution]

In the formation of the resist pattern having a LS pattern with a linewidth of 65 nm (a pitch of 130 nm) as the target size, resolution wasevaluated using the evaluation criteria shown below. The results areshown in Table 2.

(Evaluation Criteria)

A: LS pattern formed with high resolution such that an unexposed portionof the resist film was dissolved and removed, and an image with highcontrast was obtained

B: resist pattern formed with low resolution

C: no image

[Evaluation of Storage Stability]

Each of the resist compositions was stored for one month under roomtemperature.

Then, similarly to the aforementioned <Formation of resist pattern>, theresist pattern targeting a substantially 1:1 line and space (LS) patternwith a line width of 65 nm and a pitch of 130 nm is formed. The storagestability of the resist composition was evaluated using the evaluationcriteria shown below. The results are shown in Table 2.

(Evaluation Criteria)

A: LS pattern substantially formed having the targeted size

B: no image

[Measurement of Receding Angle]

An organic antireflection film composition (product name: ARC29,manufactured by Brewer Science Ltd.) was applied to an 8-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicantireflection film having a thickness of 82 nm.

Next, each of the resist compositions was spin-coated on the organicantireflection film, thereby forming a resist film having a thickness of100 nm.

Then, one drop of pure water (50 μL) was put on the surface of theresist film, and the receding angle was measured (the receding angleprior to exposure) using DROP MASTER-700 (product name; manufactured byKyowa Interface Science Co., Ltd.). The results are shown in Table 2.

TABLE 2 Component (F) Receding Chemical 65 nmLS 1M angle formula MwMw/Mn Resolution stability (°) Example A1 (F)-1A  25000 1.9 A A 68Example A2 (F)-2A  20000 1.8 A A 74 Comparative (F)-3A  20000 1.9 B B 69Example A1 Comparative (F)-4A  22000 1.8 C B 74 Example A2 Example A3(F)-5A  18000 1.8 A A 68 Example A4 (F)-6A  18000 1.9 A A 73 Example A5(F)-7A  15000 1.8 A A 67 Example A6 (F)-8A  15000 1.7 A A 67 Example A7(F)-9A  20000 1.8 A A 74 Example A8 (F)-10A 22000 2.0 A A 73 Example A9(F)-11A 22000 2.1 A A 75 Example A10 (F)-12A 25000 2.2 A A 73 ExampleA11 (F)-13A 21000 2.1 A A 70 Example A12 (F)-14A 22000 1.9 A A 74Comparative (F)-15A 14000 1.8 C B 76 Example A3

From the results shown in Table 2, it was confirmed that each of theresist compositions according to Examples A1 to A12 exhibited excellentstorage stability, and the methods of forming a resist pattern using theresist compositions according to Examples A1 to A12 enabled formation ofa negative pattern having a high resolution.

Examples B1 to B15, Comparative Examples B1 to B4

The components shown in Table 3 were mixed together and dissolved toobtain a resist composition.

TABLE 3 PEB Component Component Component Component Component Component(° C.) (A) (C) (G) (D) (F) (S) Example B1  90 (A)-1B (C)-1B (G)-1B(D)-1B (F)-1B (S)-1 [100] [10] [5.95] [4.05] [3] [3300] Example B2  90(A)-1B (C)-1B (G)-1B (D)-2B (F)-1B (S)-1 [100] [10] [7.87] [2.13] [3][3300] Example B3  90 (A)-1B (C)-1B (G)-1B (D)-3B (F)-1B (S)-1 [100][10] [11.37] [3.63] [3] [3300] Example B4  90 (A)-1B (C)-1B (G)-2B(D)-2B (F)-1B (S)-1 [100] [3] [12.45] [2.55] [3] [3300] Example B5  90(A)-2B (C)-2B (G)-1B (D)-1B (F)-1B (S)-1 [100] [10] [5.95] [4.05] [3][3300] Example B6  90 (A)-2B (C)-2B (G)-1B (D)-2B (F)-1B (S)-1 [100][10] [7.87] [2.13] [3] [3300] Example B7  90 (A)-2B (C)-2B (G)-1B (D)-3B(F)-1B (S)-1 [100] [10] [11.37] [3.63] [3] [3300] Example B8  90 (A)-2B(C)-2B (G)-2B (D)-2B (F)-1B (S)-1 [100] [3] [12.45] [2.55] [3] [3300]Example B9 110 (A)-3B (C)-1B (G)-1B (D)-2B (F)-1B (S)-1 [100] [10][7.87] [2.13] [3] [3300] Example B10 110 (A)-3B (C)-1B (G)-2B (D)-2B(F)-1B (S)-1 [100] [3] [12.45] [2.55] [3] [3300] Comparative  90 (A)-2B(C)-1B (G)-1B — (F)-1B (S)-1 Example B1 [100] [3] [4.00] [3] [3300]Comparative  90 (A)-2B (C)-1B (G)-3B — (F)-1B (S)-1 Example B2 [100] [3][4.00] [3] [3300] Comparative  90 (A)-2B (C)-2B (G)-1B (D)-1B (F)-1B(S)-1 Example B3 [100] [10] [4.00] [1.36] [3] [3300] Comparative  90(A)-2B (C)-2B (G)-1B (D)-1B (F)-1B (S)-1 Example B4 [100] [10] [4.00][2.18] [3] [3300] Example B11  90 (A)-2B (C)-2B (G)-1B (D)-1B (F)-1B(S)-1 [100] [10] [4.00] [5.45] [3] [3300] Example B12  90 (A)-2B (C)-1B(G)-3B (D)-4B (F)-1B (S)-1 [100] [3] [4.00] [0.92] [3] [3300] ExampleB13  90 (A)-2B (C)-1B (G)-3B (D)-4B (F)-1B (S)-1 [100] [3] [4.00] [1.84][3] [3300] Example B14  90 (A)-2B (C)-1B (G)-3B (D)-4B (F)-1B (S)-1[100] [3] [4.00] [4.6] [3] [3300] Example B15  90 (A)-2B (C)-1B (G)-4B(D)-1B (F)-1B (S)-1 [100] [3] [10.0] [4.27] [3] [3300]

In Table 3, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added, (S)-1 is the same as definedabove, and the reference characters other than (S)-1 indicate thefollowing. In addition, a molar ratio of the component (G) and thecomponent (D) used in each Example is shown in Table 4.

(A)-1B: a copolymer represented by chemical formula (A)-1B shown below[Mw=7,000, Mw/Mn=1.57. l/m/n=40/40/20 (the composition of the copolymer(molar ratio))].

(A)-2B: a copolymer represented by chemical formula (A)-2B shown below[Mw=7,000, Mw/Mn=1.7. l/m/n/o/p=15/17/34/21/13 (the composition of thecopolymer (molar ratio))].

(A)-3B: a copolymer represented by chemical formula (A)-3B shown below[Mw=7,000, Mw/Mn=1.57. l/m/n=45/35/20 (the composition of the copolymer(molar ratio))].

(C)-1B: a compound represented by the aforementioned chemical formula(C)-1A.

(C)-2B: a compound represented by chemical formula (C)-2B shown below.

(G)-1B: a compound represented by chemical formula (G)-1B shown below[pKa=−11.55].

(G)-2B: a compound represented by chemical formula (G)-2B shown below[pKa=−3.36].

(G)-3B: a compound represented by chemical formula (G)-3B shown below[pKa=−3.57].

(G)-4B: a compound represented by chemical formula (G)-4B shown below[pKa of anion=−3.36; pKa of cation=5.7].

(D)-1B: a heptafluorobutylamine [pKa=5.6, boiling point=69° C.].

(D)-2B: a pyridine [pKa=5.7, boiling point=115.2° C.].

(D)-3B: an aniline [pKa=4.87, boiling point=184° C.].

(D)-4B: an oxazole [pKa=0.8, boiling point=70° C.].

(F)-1B: a compound represented by chemical formula (F)-1B shown below[Mw=24,000, Mw/Mn=1.38. l=100 (the composition of the polymer (molarratio))].

<Formation of Resist Patterns>

(Step (1))

An organic antireflection film composition (product name: ARC29,manufactured by Brewer Science Ltd.) was applied to an 8-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicantireflection film having a thickness of 82 nm.

Then, each resist composition immediately after preparation thereof wasapplied using a spinner, the resist films were placed on a cooling platefor 60 seconds, thereby forming a resist film having a thickness of 100nm.

(Step (2))

Subsequently, the resist film was irradiated with an ArF excimer laser(193 nm) through a photomask (halftone) targeting a SL pattern with aspace width of 140 nm and a pitch of 280 nm, using an ArF exposureapparatus NSR-5302 (manufactured by Nikon Corporation; NA (numericalaperture)=0.60, 2/3 annular).

(Step (3))

Then, a post exposure bake (PEB) treatment was conducted at atemperature described in Table 3 for 60 seconds.

(Step (4))

Thereafter, alkali developing was conducted for 30 seconds at 23° C. ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.).

As a result, in all of the examples, patterns having contrast in theresist film were obtained so that unexposed portions of the resist filmwere dissolved.

Further, in Examples B1 to B13, and B15, 1:1 SL patterns with a spacewidth of 140 nm were resolved.

<Evaluation of Receding Angle>

An organic antireflection film composition (product name: ARC29,manufactured by Brewer Science Ltd.) was applied to an 8-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicantireflection film having a thickness of 82 nm.

Then, each resist composition immediately after preparation thereof wasapplied using a spinner, the resist films were placed on a cooling platefor 60 seconds, thereby forming a resist film having a thickness of 100nm.

A water droplet was dripped onto the surface of each resist film (theresist film prior to exposure), and a DROP MASTER-700 apparatus (aproduct name, manufactured by Kyowa Interface Science Co., Ltd.) wasused to measure the receding angle (receding angle measurement: water 50μL). The result of this measurement was referred to as the “initialreceding angle (°)”, and is shown in Table 4.

<Evaluation of Storage Stability>

The resist compositions according to Examples B1 to B11 and ComparativeExamples B1 to B4 prepared in the above-described manner were stored fortwo weeks under room temperature. Then, the receding angles weremeasured in the same manner as described above in the evaluation of thereceding angle. The result thereof was referred to as the “2w laterreceding angle (°)”, and is shown in Table 4.

TABLE 4 Initial 2w later Component (G): receding angle receding angleComponent (D) (°) (°) Example B1 1:1 67.0 67.2 Example B2 1:1 67.3 67.1Example B3 1:1 66.9 66.8 Example B4 1:1 66.6 67.1 Example B5 1:1 66.965.9 Example B6 1:1 65.9 66.3 Example B7 1:1 66.8 66.1 Example B8 1:165.7 65.9 Example B9 1:1 68.3 68.0 Example B10 1:1 68.6 67.8 Comparative1:0 68.0 64.2 Example B1 Comparative 1:0 67.3 63.8 Example B2Comparative   1:0.5 67.6 64.2 Example B3 Comparative Example B4   1:0.867.7 64.6 Example B11 1:2 66.7 66.1 Example B12 1:1 66.5 66.8 ExampleB13 1:2 67.1 66.8 Example B14 1:5 67.6 67.2 Example B15 1:1 66.4 66.5

From the results described above, it was confirmed that the resistcomposition of Examples B1 to B15 according to the present inventionreduced decrease of receding angle in the resist composition storedunder room temperature and exhibited excellent storage stability ascompared to the resist composition of Comparative Examples B1 to B2containing no amine and to the resist composition of ComparativeExamples B3 to B4 containing less amine than the acidic compound.

Examples C1 to C10, Comparative Examples C1 to C4

The components shown in Table 5 were mixed together and dissolved toobtain a resist composition.

TABLE 5 Compo- Compo- Compo- Compo- Compo- nent nent nent nent nent A(C) (G1C) (F) (S) Example (A)-1C (C)-1C (G)-1C (F)-1C (S)-1 C1 [100][10] [10] [3] [3300] Example (A)-1C (C)-1C (G)-2C (F)-1C (S)-1 C2 [100][10] [10] [3] [3300] Example (A)-1C (C)-1C (G)-3C (F)-1C (S)-1 C3 [100][10] [10] [3] [3300] Example (A)-1C (C)-1C (G)-4C (F)-1C (S)-1 C4 [100][3]  [15] [3] [3300] Example (A)-2C (C)-2C (G)-1C (F)-1C (S)-1 C5 [100][10] [10] [3] [3300] Example (A)-2C (C)-2C (G)-2C (F)-1C (S)-1 C6 [100][10] [10] [3] [3300] Example (A)-2C (C)-2C (G)-3C (F)-1C (S)-1 C7 [100][10] [10] [3] [3300] Example (A)-2C (C)-2C (G)-4C (F)-1C (S)-1 C8 [100][3]  [15] [3] [3300] Example (A)-3C (C)-1C (G)-2C (F)-1C (S)-1 C9 [100][10] [10] [3] [3300] Example (A)-3C (C)-1C (G)-4C (F)-1C (S)-1 C10 [100][3]  [15] [3] [3300] Comparative (A)-3C (C)-1C (G)-AC (F)-1C (S)-1Example C1 [100] [3]  [4]  [3] [3300] Comparative (A)-3C (C)-1C (G)-BC(F)-1C (S)-1 Example C2 [100] [3]  [4]  [3] [3300] Comparative (A)-2C(C)-2C (G)-CC (F)-1C (S)-1 Example C3 [100] [10] [10] [3] [3300]Comparative (A)-2C (C)-2C (G)-DC (F)-1C (S)-1 Example C4 [100] [10] [10][3] [3300]

In Table 5, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added, (S)-1 is the same as definedabove, and the reference characters other than (S)-1 indicate thefollowing.

(A)-1C: the same copolymer as (A)-1B described above.

(A)-2C: the same copolymer as (A)-2B described above.

(A)-3C: the same copolymer as (A)-3B described above.

(C)-1C: a compound represented by the aforementioned chemical formula(C)-1A.

(C)-2C: a compound represented by the aforementioned chemical formula(C)-2B.

(G)-1C: a compound represented by chemical formula (G)-1C shown below[pKa of cation=5.6, pKa of anion=−11.55].

(G)-2C: a compound represented by the aforementioned chemical formula(G)-1A [pKa of cation=5.7, pKa of anion=−11.55].

(G)-3C: a compound represented by chemical formula (G)-3C shown below[pKa of cation=4.87, pKa of anion=−11.55].

(G)-4C: a compound represented by chemical formula (G)-4C shown below[pKa of cation=5.7, pKa of anion=−3.36].

(G)-AC: the same compound as (G)-1B described above [pKa=−11.55].

(G)-BC: the same compound as (G)-3B described above [pKa=−3.57].

(G)-CC: a compound represented by chemical formula (G)-CC shown below[pKa of cation=10.7, pKa of anion=−11.55].

(G)-DC: a compound represented by chemical formula (G)-DC shown below[pKa of cation=7.77, pKa of anion=−11.55].

(F)-1C: the same compound as (F)-1B described above.

<Formation of Resist Patterns 1>

(Step (1))

An organic antireflection film composition (product name: ARC29,manufactured by Brewer Science Ltd.) was applied to an 8-inch siliconwafer using a spinner, and the composition was then baked and dried on ahotplate at 205° C. for 60 seconds, thereby forming an organicantireflection film having a thickness of 82 nm.

Then, each resist composition immediately after preparation thereof wasapplied using a spinner, the resist films were dried such that theresist compositions of Examples C9 to C10 and Comparative Examples C1 toC2 were prebaked (PAB) at 80° C. for 60 seconds, or such that the otherresist compositions were placed on a cooling plate at 23° C. for 60seconds, thereby forming a resist film having a thickness of 100 nm.

(Step (2))

Subsequently, the resist film was irradiated with an ArF excimer laser(193 nm) through a photomask (halftone) targeting a SL pattern with aspace width of 130 nm and a pitch of 260 nm, using an ArF exposureapparatus NSR-5302 (manufactured by Nikon Corporation; NA (numericalaperture)=0.60, 2/3 annular).

(Step (3))

Then, a post exposure bake (PEB) treatment was conducted at atemperature indicated in Table 6 for 60 seconds.

(Step (4))

Thereafter, alkali developing was conducted for 30 seconds at 23° C. ina 2.38% by weight aqueous solution of tetramethylammonium hydroxide(TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co.,Ltd.).

As a result, in the examples except Comparative Examples C3 to C4, 1:1SL patterns with a space width of 130 were formed in the resist films.The optimum exposure dose Eop (mJ/cm²; sensitivity) with which the SLpattern was formed was determined. The result thereof was referred to asthe “initial sensitivity”, and is shown in Table 6.

<Evaluation of Receding Angle 1>

Next, similarly to the formation of resist pattern 1 described above,the resist films were formed using the resist compositions of ExamplesC1 to C10 and Comparative Examples C1 to C4.

A water droplet was dripped onto the surface of each resist film (theresist film prior to exposure), and a DROP MASTER-700 apparatus (aproduct name, manufactured by Kyowa Interface Science Co., Ltd.) wasused to measure the receding angle (receding angle measurement: water 50μL). The result of this measurement was referred to as the “initialreceding angle (°)”, and is shown in Table 6.

<Evaluation of Storage Stability 1>

The resist compositions according to Examples C1 to C10 and ComparativeExamples C1 to C4 prepared in the above-described manner were stored fortwo weeks under room temperature. Then, the receding angles weremeasured in the same manner as described above in the evaluation of thereceding angle 1. The result thereof was referred to as the “2w laterreceding angle (°)”, and is shown in Table 6.

Further, the resist compositions according to Examples C1 to C10 andComparative Examples C1 to C4 prepared in the above-described mannerwere stored for two weeks under room temperature. Then, similarly to theformation of resist pattern 1 described above, the resist patterns wereformed, and the optimum exposure dose was determined. The result thereofwas referred to as the “2w later sensitivity”, and is shown in Table 6.Here, in Comparative Examples C3 to C4, since 1:1 SL patterns with aspace width of 130 were not resolved, patters were not formed similarlyto the results described above.

TABLE 6 Initial 2w later receding receding Initial 2w later PEB angleangle sensitivity sensitivity (° C.) (°) (°) (mJ/cm²) (mJ/cm²) ExampleC1 90 67.0 67.2 17 19 Example C2 90 67.3 67.1 20 22 Example C3 90 66.966.8 21 23 Example C4 90 66.6 67.1 34 35 Example C5 90 66.9 65.9 19 21Example C6 90 65.9 66.3 22 23 Example C7 90 66.8 66.1 23 24 Example C890 65.7 65.9 37 39 Example C9 110 68.3 68.0 72 74 Example C10 110 68.667.8 75 77 Comparative 110 68.0 64.2 86 >100 Example C1 Comparative 11067.3 63.8 90 >100 Example C2 Comparative 90 67.6 66.5 No image ExampleC3 Comparative 90 66.7 66.1 No image Example C4

From the results described above, it was confirmed that the resistcomposition of Examples C1 to C10 according to the present inventionexhibited excellent resolution as compared to the resist composition ofComparative Examples C3 to C4 including an acidic compound containing acation having a pKa value more than 7.

In addition, it was confirmed that the resist composition of Examples C1to C10 according to the present invention exhibited excellent storagestability so that decrease of receding angle and slowdown of sensitivitywere reduced after storage as compared to the resist composition ofComparative Examples C1 to C2 including an acidic compound which doesnot form a salt.

Examples C11 to C20

The components shown in Table 7 were mixed together and dissolved toobtain a resist composition.

TABLE 7 Component Component Component Component Component Component (A)(C) (G1) (D) (F) (S) Example (A)-1C (C)-1C (G)-4C (D)-1C (F)-1C (S)-1C11 [100] [3] [10] [5] [3] [3300] Example (A)-1C (C)-1C (G)-4C (D)-1C(F)-1C (S)-1 C12 [100] [3] [10] [15] [3] [3300] Example (A)-1C (C)-1C(G)-1C (D)-1C (F)-1C (S)-1 C13 [100] [10] [10] [5] [3] [3300] Example(A)-1C (C)-1C (G)-1C (D)-1C (F)-1C (S)-1 C14 [100] [10] [10] [15] [3][3300] Example (A)-1C (C)-1C (G)-1C (D)-2C (F)-1C (S)-1 C15 [100] [10][10] [5] [3] [3300] Example (A)-1C (C)-1C (G)-1C (D)-2C (F)-1C (S)-1 C16[100] [10] [10] [15] [3] [3300] Example (A)-2C (C)-1C (G)-4C (D)-1C(F)-1C (S)-1 C17 [100] [3] [10] [5] [3] [3300] Example (A)-2C (C)-1C(G)-4C (D)-1C (F)-1C (S)-1 C18 [100] [3] [10] [15] [3] [3300] Example(A)-3C (C)-1C (G)-1C (D)-2C (F)-1C (S)-1 C19 [100] [10] [10] [5] [3][3300] Example (A)-3C (C)-1C (G)-1C (D)-2C (F)-1C (S)-1 C20 [100] [10][10] [15] [3] [3300]

In Table 7, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added, (A)-1C to 3C, (C)-1C, (G)-1C,(G)-4C, (F)-1C and (S)-1 are the same as defined above, and thereference characters other than these indicate the following.

(D)-1C: the same as (D)-1B described above, a heptafluorobutylamine[pKa=5.6, boiling point=69° C.].

(D)-2C: a trifluoroethylamine [pKa=5.7, boiling point=37° C.].

<Formation of Resist Patterns 2>

In the same manner as the formation of resist pattern 1 described above(provided that, in film formation, all of the examples were notsubjected to a prebake treatment, and were placed on a cooling plate at23° C. for 60 seconds), 1:1 SL patterns with a space width of 130 nm anda pitch of 260 nm were formed. As a result, in all of the examples, SLpatterns were formed. The optimum exposure dose Eop (mJ/cm²;sensitivity) with which the SL pattern was formed was determined. Theresult thereof was referred to as the “initial sensitivity”, and isshown in Table 8.

<Evaluation of Receding Angle 2> <Evaluation of Storage Stability 2>

In the same manner as the evaluation of receding angle 1 and theevaluation of storage stability 1 described above, the initial recedingangle, and two weeks later receding angle and sensitivity were obtained.The results are shown in Table 8.

TABLE 8 Initial 2w later receding receding Initial 2w later PEB angleangle sensitivity sensitivity (° C.) (°) (°) (mJ/cm²) (mJ/cm²) Example90 67.1 67.3 32 31 C11 Example 90 66.7 66.5 28 28 C12 Example 90 67.467.3 17 16 C13 Example 90 66.2 66.3 15 15 C14 Example 90 67.6 67.0 16 15C15 Example 90 66.9 66.9 14 14 C16 Example 90 66.5 66.0 35 34 C17Example 90 66.0 66.2 32 32 C18 Example 110 67.1 67.0 65 64 C19 Example110 67.3 67.0 63 63 C20

From the results described above, it was confirmed that the resistcomposition of Examples C11 to C20 according to the present inventionexhibited excellent storage stability without decrease of receding angleand slowdown of sensitivity after storage.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. A method of forming a resist pattern, comprising:a step (1) in which a resist composition comprising a base component (A)that exhibits increased solubility in an alkali developing solutionunder the action of acid, a photo-base generator component (C) thatgenerates a base upon exposure, an acid supply component (Z) and acompound (F) containing at least one selected from the group consistingof a fluorine atom and a silicon atom is applied to a substrate to forma resist film; a step (2) in which the resist film is subjected toexposure; a step (3) in which baking is conducted after the step (2),such that, at an exposed portion of the resist film, the base generatedfrom the photo-base generator component (C) upon the exposure and anacid derived from the acid supply component (Z) are neutralized, and atan unexposed portion of the resist film, the solubility of the basecomponent (A) in an alkali developing solution is increased by theaction of the acid derived from the acid supply component (Z); and astep (4) in which the resist film is subjected to an alkali development,thereby forming a negative-tone resist pattern in which the unexposedportion of the resist film has been dissolved and removed, wherein thecompound (F) contains no acid decomposable group which exhibitsincreased polarity by the action of acid.
 2. The method according toclaim 1, wherein the compound (F) contains a polymer having a structuralunit represented by general formula (f1-1) shown below, or a compoundrepresented by general formula (f11-1) shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; A represents—O— or —NH—; X₀ represents a single bond or a divalent linking group; R₀represents an organic group; at least one of X₀ and R₀ contains afluorine atom or a silicon atom; and v is 0 or
 1. 3. The methodaccording to claim 1, wherein the acid supply component (Z) comprises anacidic compound component (G).
 4. The method according to claim 3,wherein the resist composition further comprises an amine (D).
 5. Themethod according to claim 3, wherein the acidic compound component (G)includes an acid salt component (G1) having an acid strength capable ofincreasing the solubility of the base component (A) in an alkalideveloping solution.
 6. The method according to claim 5, wherein thecomponent (G1) is an ionic compound composed of a nitrogen-containingcation and a counteranion.
 7. The method according to claim 5, whereinthe component (G1) is an ionic compound composed of a cation moietyrepresented by general formula (G1c-1) shown below and a counteranion:

wherein R^(101d), R^(101e), R^(101f) and R^(101g) each independentlyrepresents a hydrogen atom, a linear, branched or cyclic alkyl group, analkenyl group, an oxoalkyl group or an oxoalkenyl group of 1 to 12carbon atoms, an aryl group or an arylalkyl group of 6 to 20 carbonatoms, an aralkyl group of 7 to 12 carbon atoms or an aryloxoalkylgroup, and part or all of the hydrogen atoms of these groups may besubstituted with a halogen atom, an alkoxy group or a sulfur atom.R^(101d) and R^(101e), or R^(101d), R_(101e) and R^(101f) may bemutually bonded with the nitrogen atom to form a ring, provided that,when a ring is formed, each of R^(101d) and R^(101e), or each ofR^(101d), R^(101e) and R^(101f) independently represents an alkylenegroup of 3 to 10 carbon atoms, or forms a heteroaromatic ring containingthe nitrogen atom in the ring thereof.
 8. The method according to claim5, wherein the component (G1) is an ionic compound comprising: anitrogen-containing cation; and a counteranion having at least one aniongroup selected from the group consisting of a sulfonate anion, acarboxylate anion, a sulfonylimide anion, a bis(alkylsulfonyl)imideanion and a tris(alkylsulfonyl)methide anion.
 9. A method of forming aresist pattern, comprising: a step (1) in which a resist compositioncomprising a base component (A) that exhibits increased solubility in analkali developing solution under the action of acid, a photo-basegenerator component (C) that generates a base upon exposure, an acidiccompound component (G) and an amine (D) is applied to a substrate toform a resist film; a step (2) in which the resist film is subjected toexposure; a step (3) in which baking is conducted after the step (2),such that, at an exposed portion of the resist film, the base generatedfrom the photo-base generator component (C) upon the exposure and theacidic compound component (G) are neutralized, and at an unexposedportion of the resist film, the solubility of the base component (A) inan alkali developing solution is increased by the action of the acidiccompound component (G); and a step (4) in which the resist film issubjected to an alkali development, thereby forming a negative-toneresist pattern in which the unexposed portion of the resist film hasbeen dissolved and removed, wherein the amount of the amine (D) is 1 molor more, per 1 mol of the acidic compound component (G).
 10. The methodaccording to claim 9, wherein the amount of the amine (D) is 1 to 10mol, per 1 mol of the acidic compound component (G).
 11. A method offorming a resist pattern, comprising: a step (1) in which a resistcomposition comprising a base component (A) that exhibits increasedsolubility in an alkali developing solution under the action of acid, aphoto-base generator component (C) that generates a base upon exposure,and an acidic compound component (G) is applied to a substrate to form aresist film; a step (2) in which the resist film is subjected toexposure; a step (3) in which baking is conducted after the step (2),such that, at an exposed portion of the resist film, the base generatedfrom the photo-base generator component (C) upon the exposure and theacidic compound component (G) are neutralized, and at an unexposedportion of the resist film, the solubility of the base component (A) inan alkali developing solution is increased by the action of the acidiccompound component (G); and a step (4) in which the resist film issubjected to an alkali development, thereby forming a negative-toneresist pattern in which the unexposed portion of the resist film hasbeen dissolved and removed, wherein the acidic compound component (G)comprises a compound (G1C) composed of a nitrogen-containing cationhaving a pKa value of 7 or less and a counteranion.
 12. The methodaccording to claim 11, wherein the resist composition further comprisesan amine (D).